diff --git a/0_python/1_Basics.ipynb b/0_python/1_Basics.ipynb
index 01010da..73cde70 100644
--- a/0_python/1_Basics.ipynb
+++ b/0_python/1_Basics.ipynb
@@ -165,7 +165,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -174,7 +174,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -220,7 +220,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -229,7 +229,7 @@
        "3"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 6,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -240,7 +240,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [
     {
@@ -249,7 +249,7 @@
        "1"
       ]
      },
-     "execution_count": 5,
+     "execution_count": 7,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -347,7 +347,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
@@ -356,7 +356,7 @@
        "5"
       ]
      },
-     "execution_count": 10,
+     "execution_count": 9,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -374,7 +374,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [
     {
@@ -383,7 +383,7 @@
        "1.0"
       ]
      },
-     "execution_count": 11,
+     "execution_count": 10,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -485,7 +485,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -495,7 +495,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
@@ -514,7 +514,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [
     {
@@ -523,7 +523,7 @@
        "2"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 13,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -604,7 +604,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -613,7 +613,7 @@
        "'0xaa'"
       ]
      },
-     "execution_count": 20,
+     "execution_count": 14,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -624,7 +624,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -633,7 +633,7 @@
        "170"
       ]
      },
-     "execution_count": 21,
+     "execution_count": 15,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -644,7 +644,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
     {
@@ -653,7 +653,7 @@
        "'0o10'"
       ]
      },
-     "execution_count": 22,
+     "execution_count": 16,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -671,7 +671,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [
     {
@@ -699,7 +699,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [
     {
@@ -807,7 +807,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -832,7 +832,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -841,7 +841,7 @@
        "(4, 1)"
       ]
      },
-     "execution_count": 28,
+     "execution_count": 20,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -917,7 +917,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [
     {
@@ -943,7 +943,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [
     {
@@ -978,14 +978,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": 25,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Type something here and it will be stored in variable abc \t10\n"
+      "Type something here and it will be stored in variable abc \t20\n"
      ]
     }
    ],
@@ -995,7 +995,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [
     {
@@ -1004,7 +1004,7 @@
        "str"
       ]
      },
-     "execution_count": 33,
+     "execution_count": 26,
      "metadata": {},
      "output_type": "execute_result"
     }
diff --git a/0_python/2_Print_Statement.ipynb b/0_python/2_Print_Statement.ipynb
index 16c2bfe..4d9b5e9 100644
--- a/0_python/2_Print_Statement.ipynb
+++ b/0_python/2_Print_Statement.ipynb
@@ -47,7 +47,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -98,7 +98,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 3,
    "metadata": {
     "scrolled": true
    },
@@ -129,7 +129,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -153,7 +153,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -186,7 +186,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -218,7 +218,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
@@ -249,7 +249,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [
     {
@@ -266,7 +266,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [
     {
@@ -283,7 +283,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
@@ -307,7 +307,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [
     {
@@ -331,7 +331,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -348,7 +348,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -390,7 +390,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
     {
@@ -399,7 +399,7 @@
        "'3.121312'"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 16,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -417,7 +417,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [
     {
@@ -426,7 +426,7 @@
        "'3.12131'"
       ]
      },
-     "execution_count": 19,
+     "execution_count": 17,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -444,7 +444,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [
     {
@@ -453,7 +453,7 @@
        "'-33.12131'"
       ]
      },
-     "execution_count": 25,
+     "execution_count": 18,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -471,7 +471,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -480,7 +480,7 @@
        "'00000000000003.12131'"
       ]
      },
-     "execution_count": 17,
+     "execution_count": 19,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -498,7 +498,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [
     {
@@ -511,8 +511,8 @@
     }
    ],
    "source": [
-    "print \"% 9f\" % 3.121312312312\n",
-    "print \"% 9f\" % -3.121312312312"
+    "print(\"% 9f\" % 3.121312312312)\n",
+    "print(\"% 9f\" % -3.121312312312)"
    ]
   },
   {
@@ -524,7 +524,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
@@ -537,8 +537,8 @@
     }
    ],
    "source": [
-    "print \"%+9f\" % 3.121312312312\n",
-    "print \"% 9f\" % -3.121312312312"
+    "print(\"%+9f\" % 3.121312312312)\n",
+    "print(\"% 9f\" % -3.121312312312)"
    ]
   },
   {
diff --git a/0_python/3_Data_Structure_1.ipynb b/0_python/3_Data_Structure_1.ipynb
index 37b2966..d01b00e 100644
--- a/0_python/3_Data_Structure_1.ipynb
+++ b/0_python/3_Data_Structure_1.ipynb
@@ -65,7 +65,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -97,7 +97,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -106,7 +106,7 @@
        "'apple'"
       ]
      },
-     "execution_count": 2,
+     "execution_count": 4,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -124,7 +124,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -133,7 +133,7 @@
        "'peach'"
       ]
      },
-     "execution_count": 4,
+     "execution_count": 5,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -151,7 +151,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -167,19 +167,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[['apple', 'orange', 'peach'], ['carrot', 'potato']]\n"
+      "[['apple', 'orange', 'peach'], ['carrot', 'potato'], 'Test']\n"
      ]
     }
    ],
    "source": [
-    "z  = [x,y]\n",
+    "z  = [x,y, 'Test']\n",
     "print(z)"
    ]
   },
@@ -215,7 +215,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
@@ -240,7 +240,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [
     {
@@ -249,7 +249,7 @@
        "'apple'"
       ]
      },
-     "execution_count": 9,
+     "execution_count": 10,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -267,7 +267,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [
     {
@@ -276,7 +276,7 @@
        "'apple'"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 11,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -310,7 +310,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -319,6 +319,7 @@
      "text": [
       "[3, 2, 3]\n",
       "[2, 3, 2, 3, 4, 5, 6, 7, 8, 9]\n",
+      "[2, 3, 2, 3, 4, 5, 6, 7, 8, 9]\n",
       "[2, 3, 2, 3, 4, 5, 6, 7, 8, 9]\n"
      ]
     }
@@ -327,12 +328,13 @@
     "num = [2,3,2,3,4,5,6,7,8,9]\n",
     "print(num[1:4])\n",
     "print(num[0:])\n",
-    "print(num[:])"
+    "print(num[:])\n",
+    "print(num)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -358,7 +360,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
     {
@@ -367,7 +369,7 @@
        "[2, 3, 6]"
       ]
      },
-     "execution_count": 15,
+     "execution_count": 16,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -392,7 +394,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [
     {
@@ -401,7 +403,7 @@
        "10"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 17,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -419,27 +421,35 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[2, 3, 2, 3, 4, 5, 6, 7, 8, 9]\n"
+     ]
+    },
+    {
      "data": {
       "text/plain": [
-       "0"
+       "2"
       ]
      },
-     "execution_count": 14,
+     "execution_count": 20,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
+    "print(num)\n",
     "min(num)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -448,7 +458,7 @@
        "9"
       ]
      },
-     "execution_count": 15,
+     "execution_count": 19,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -466,7 +476,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [
     {
@@ -475,7 +485,7 @@
        "[1, 2, 3, 5, 4, 7]"
       ]
      },
-     "execution_count": 16,
+     "execution_count": 21,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -493,7 +503,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -509,7 +519,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
@@ -518,7 +528,7 @@
        "False"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 23,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -596,7 +606,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -605,7 +615,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 25,
    "metadata": {},
    "outputs": [
     {
@@ -631,7 +641,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -640,7 +650,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [
     {
@@ -673,7 +683,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [
     {
@@ -704,7 +714,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 29,
    "metadata": {},
    "outputs": [
     {
@@ -713,7 +723,7 @@
        "['h', 'e', 'l', 'l', 'o']"
       ]
      },
-     "execution_count": 24,
+     "execution_count": 29,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -731,7 +741,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 44,
+   "execution_count": 30,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -740,7 +750,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 45,
+   "execution_count": 31,
    "metadata": {},
    "outputs": [
     {
@@ -765,7 +775,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 32,
    "metadata": {},
    "outputs": [
     {
@@ -774,7 +784,7 @@
        "3"
       ]
      },
-     "execution_count": 46,
+     "execution_count": 32,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -792,7 +802,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 33,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -801,15 +811,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 35,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 4, 8, 7, 1, [5, 4, 2, 8]]\n"
+      "[1, 1, 4, 8, 7, 1, [5, 4, 2, 8], [5, 4, 2, 8]]\n"
      ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "[1, 1, 4, 8, 7, 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2, 8]"
+      ]
+     },
+     "execution_count": 35,
+     "metadata": {},
+     "output_type": "execute_result"
     }
    ],
    "source": [
@@ -826,14 +846,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 36,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 4, 8, 7, 1, [5, 4, 2, 8], 5, 4, 2, 8]\n"
+      "[1, 1, 4, 8, 7, 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2, 8]\n"
      ]
     }
    ],
@@ -851,7 +871,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 37,
    "metadata": {},
    "outputs": [
     {
@@ -860,7 +880,7 @@
        "0"
       ]
      },
-     "execution_count": 50,
+     "execution_count": 37,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -871,7 +891,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 38,
    "metadata": {},
    "outputs": [
     {
@@ -879,9 +899,9 @@
      "evalue": "999 is not in list",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-51-344da5bcf759>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlst\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m999\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mValueError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-38-344da5bcf759>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlst\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m999\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
       "\u001b[0;31mValueError\u001b[0m: 999 is not in list"
      ]
     }
@@ -899,14 +919,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 39,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 4, 8, 7, 'name', 1, [5, 4, 2, 8], 5, 4, 2, 8]\n"
+      "[1, 1, 4, 8, 7, 'name', 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2, 8]\n"
      ]
     }
    ],
@@ -924,14 +944,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 53,
+   "execution_count": 40,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 4, 8, 7, 'Python', 1, [5, 4, 2, 8], 5, 4, 2, 8]\n"
+      "[1, 1, 4, 8, 7, 'Python', 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2, 8]\n"
      ]
     }
    ],
@@ -949,16 +969,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 54,
+   "execution_count": 41,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "[1, 1, 4, 8, 7, 'Python', 1, [5, 4, 2, 8], 5, 4, 2]"
+       "[1, 1, 4, 8, 7, 'Python', 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2]"
       ]
      },
-     "execution_count": 54,
+     "execution_count": 41,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -977,7 +997,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 55,
+   "execution_count": 42,
    "metadata": {},
    "outputs": [
     {
@@ -986,7 +1006,7 @@
        "4"
       ]
      },
-     "execution_count": 55,
+     "execution_count": 42,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -997,14 +1017,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 57,
+   "execution_count": 43,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 8, 7, 'Python', 1, [5, 4, 2, 8], 5, 4, 2]\n"
+      "[1, 1, 8, 7, 'Python', 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 4, 2]\n"
      ]
     },
     {
@@ -1013,7 +1033,7 @@
        "4"
       ]
      },
-     "execution_count": 57,
+     "execution_count": 43,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1025,14 +1045,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 58,
+   "execution_count": 44,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 8, 7, 'Python', 1, [5, 4, 2, 8], 5, 2]\n"
+      "[1, 1, 8, 7, 'Python', 1, [5, 4, 2, 8], [5, 4, 2, 8], 5, 2]\n"
      ]
     }
    ],
@@ -1049,14 +1069,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 60,
+   "execution_count": 46,
    "metadata": {},
    "outputs": [
     {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[1, 1, 8, 7, 1, [5, 4, 2, 8], 5, 2]\n"
+     "ename": "ValueError",
+     "evalue": "list.remove(x): x not in list",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mValueError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-46-77711ca19f77>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlst\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mremove\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Python'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mlst\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mValueError\u001b[0m: list.remove(x): x not in list"
      ]
     }
    ],
@@ -1074,15 +1098,15 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 61,
+   "execution_count": 52,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[1, 1, 8, 7, 1, [5, 4, 2, 8], 5, 2]\n",
-      "[1, 8, 7, 1, [5, 4, 2, 8], 5, 2]\n"
+      "[1, [5, 4, 2, 8], 5, 2]\n",
+      "[1, 5, 2]\n"
      ]
     }
    ],
@@ -1101,14 +1125,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 62,
+   "execution_count": 53,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[2, 5, [5, 4, 2, 8], 1, 7, 8, 1]\n"
+      "[2, 5, 1]\n"
      ]
     }
    ],
@@ -1128,7 +1152,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 63,
+   "execution_count": 54,
    "metadata": {},
    "outputs": [
     {
@@ -1154,14 +1178,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 64,
+   "execution_count": 56,
    "metadata": {},
    "outputs": [
     {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[10, 8, 8, 4, 1]\n"
+     "ename": "TypeError",
+     "evalue": "must use keyword argument for key function",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-56-2b0ae825b0c3>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlst\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msort\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mlst\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mTypeError\u001b[0m: must use keyword argument for key function"
      ]
     }
    ],
@@ -1179,7 +1207,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 65,
+   "execution_count": 57,
    "metadata": {},
    "outputs": [
     {
@@ -1208,7 +1236,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 58,
    "metadata": {},
    "outputs": [
     {
@@ -1243,7 +1271,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 66,
+   "execution_count": 59,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1252,7 +1280,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 67,
+   "execution_count": 60,
    "metadata": {},
    "outputs": [
     {
@@ -1277,7 +1305,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 68,
+   "execution_count": 61,
    "metadata": {},
    "outputs": [
     {
@@ -1298,7 +1326,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 69,
+   "execution_count": 62,
    "metadata": {},
    "outputs": [
     {
@@ -1324,7 +1352,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 71,
+   "execution_count": 63,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1333,7 +1361,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 72,
+   "execution_count": 64,
    "metadata": {},
    "outputs": [
     {
@@ -1351,7 +1379,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 73,
+   "execution_count": 65,
    "metadata": {},
    "outputs": [
     {
@@ -1372,7 +1400,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 74,
+   "execution_count": 66,
    "metadata": {},
    "outputs": [
     {
@@ -1410,7 +1438,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 68,
    "metadata": {},
    "outputs": [
     {
@@ -1420,12 +1448,24 @@
       "(3, 1)\n",
       "<class 'tuple'>\n"
      ]
+    },
+    {
+     "ename": "TypeError",
+     "evalue": "'tuple' object does not support item assignment",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-68-9f8df9d106cc>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mxyz\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mtype\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mxyz\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 4\u001b[0;31m \u001b[0mxyz\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0;36m0\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;36m10\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m: 'tuple' object does not support item assignment"
+     ]
     }
    ],
    "source": [
     "xyz = divmod(10,3)\n",
     "print(xyz)\n",
-    "print(type(xyz))"
+    "print(type(xyz))\n",
+    "xyz[0]=10"
    ]
   },
   {
@@ -1444,7 +1484,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 75,
+   "execution_count": 69,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1461,7 +1501,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 76,
+   "execution_count": 74,
    "metadata": {},
    "outputs": [
     {
@@ -1470,7 +1510,7 @@
        "(27,)"
       ]
      },
-     "execution_count": 76,
+     "execution_count": 74,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1488,7 +1528,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 79,
+   "execution_count": 75,
    "metadata": {},
    "outputs": [
     {
@@ -1497,7 +1537,7 @@
        "(27, 27)"
       ]
      },
-     "execution_count": 79,
+     "execution_count": 75,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1515,7 +1555,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 80,
+   "execution_count": 76,
    "metadata": {
     "scrolled": true
    },
@@ -1545,7 +1585,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 81,
+   "execution_count": 77,
    "metadata": {},
    "outputs": [
     {
@@ -1572,7 +1612,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 82,
+   "execution_count": 80,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1598,7 +1638,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 58,
+   "execution_count": 81,
    "metadata": {},
    "outputs": [
     {
@@ -1630,7 +1670,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 59,
+   "execution_count": 82,
    "metadata": {},
    "outputs": [
     {
@@ -1639,7 +1679,7 @@
        "3"
       ]
      },
-     "execution_count": 59,
+     "execution_count": 82,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1657,7 +1697,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 60,
+   "execution_count": 83,
    "metadata": {},
    "outputs": [
     {
@@ -1666,7 +1706,7 @@
        "1"
       ]
      },
-     "execution_count": 60,
+     "execution_count": 83,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1693,7 +1733,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 83,
+   "execution_count": 85,
    "metadata": {},
    "outputs": [
     {
@@ -1711,7 +1751,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 84,
+   "execution_count": 87,
    "metadata": {},
    "outputs": [
     {
@@ -1729,7 +1769,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 86,
+   "execution_count": 88,
    "metadata": {},
    "outputs": [
     {
@@ -1761,7 +1801,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 87,
+   "execution_count": 89,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1770,7 +1810,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 88,
+   "execution_count": 90,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1786,7 +1826,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 89,
+   "execution_count": 91,
    "metadata": {},
    "outputs": [
     {
@@ -1795,7 +1835,7 @@
        "{1, 2, 3, 4, 5}"
       ]
      },
-     "execution_count": 89,
+     "execution_count": 91,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1813,7 +1853,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 90,
+   "execution_count": 92,
    "metadata": {},
    "outputs": [
     {
@@ -1829,7 +1869,7 @@
        "{0, 1, 2, 3}"
       ]
      },
-     "execution_count": 90,
+     "execution_count": 92,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1849,7 +1889,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 91,
+   "execution_count": 93,
    "metadata": {},
    "outputs": [
     {
@@ -1858,7 +1898,7 @@
        "{2, 3}"
       ]
      },
-     "execution_count": 91,
+     "execution_count": 93,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1876,7 +1916,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 93,
+   "execution_count": 94,
    "metadata": {},
    "outputs": [
     {
@@ -1893,7 +1933,7 @@
        "{0, 1}"
       ]
      },
-     "execution_count": 93,
+     "execution_count": 94,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1913,7 +1953,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 94,
+   "execution_count": 95,
    "metadata": {},
    "outputs": [
     {
@@ -1922,7 +1962,7 @@
        "{0, 1, 4, 5}"
       ]
      },
-     "execution_count": 94,
+     "execution_count": 95,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1940,7 +1980,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 95,
+   "execution_count": 96,
    "metadata": {},
    "outputs": [
     {
@@ -1949,7 +1989,7 @@
        "False"
       ]
      },
-     "execution_count": 95,
+     "execution_count": 96,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1960,7 +2000,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 96,
+   "execution_count": 97,
    "metadata": {},
    "outputs": [
     {
@@ -1969,7 +2009,7 @@
        "False"
       ]
      },
-     "execution_count": 96,
+     "execution_count": 97,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -2007,14 +2047,23 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 98,
+   "execution_count": 115,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "set1=set([10, 9, 1, 2, 4])"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 113,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "{1, 2, 3}\n"
+      "set()\n"
      ]
     }
    ],
@@ -2032,16 +2081,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 99,
+   "execution_count": 116,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "{1, 3}"
+       "{1, 4, 9, 10}"
       ]
      },
-     "execution_count": 99,
+     "execution_count": 116,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -2060,7 +2109,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 100,
+   "execution_count": 117,
    "metadata": {},
    "outputs": [
     {
@@ -2069,7 +2118,7 @@
        "set()"
       ]
      },
-     "execution_count": 100,
+     "execution_count": 117,
      "metadata": {},
      "output_type": "execute_result"
     }
diff --git a/0_python/4_Data_Structure_2.ipynb b/0_python/4_Data_Structure_2.ipynb
index 62bd8e8..0b5f648 100644
--- a/0_python/4_Data_Structure_2.ipynb
+++ b/0_python/4_Data_Structure_2.ipynb
@@ -18,7 +18,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -94,7 +94,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -122,7 +122,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -146,7 +146,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -172,7 +172,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -197,7 +197,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [
     {
@@ -206,7 +206,7 @@
        "'                        Taj Mahal is beautiful                        '"
       ]
      },
-     "execution_count": 11,
+     "execution_count": 7,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -224,7 +224,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [
     {
@@ -233,7 +233,7 @@
        "'------------------------Taj Mahal is beautiful------------------------'"
       ]
      },
-     "execution_count": 12,
+     "execution_count": 8,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -251,7 +251,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
@@ -260,7 +260,7 @@
        "'00000000Taj Mahal is beautiful'"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 9,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -278,7 +278,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [
     {
@@ -287,7 +287,7 @@
      "text": [
       "h\te\tl\tl\to\n",
       "h e l l o\n",
-      "h       e       l       l       o\n"
+      "h   e   l   l   o\n"
      ]
     }
    ],
@@ -295,7 +295,7 @@
     "s = 'h\\te\\tl\\tl\\to'\n",
     "print(s)\n",
     "print(s.expandtabs(1))\n",
-    "print(s.expandtabs())"
+    "print(s.expandtabs(4))"
    ]
   },
   {
@@ -309,7 +309,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [
     {
@@ -325,9 +325,9 @@
      "evalue": "substring not found",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-15-a7d6b97b4839>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Taj'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m0\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m10\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m20\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mValueError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-13-a7d6b97b4839>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Taj'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m0\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m10\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m20\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
       "\u001b[0;31mValueError\u001b[0m: substring not found"
      ]
     }
@@ -347,7 +347,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -371,7 +371,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -397,7 +397,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
     {
@@ -423,7 +423,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [
     {
@@ -432,7 +432,7 @@
        "'*a_a-'"
       ]
      },
-     "execution_count": 19,
+     "execution_count": 17,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -443,7 +443,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [
     {
@@ -452,7 +452,7 @@
        "'1\\n2'"
       ]
      },
-     "execution_count": 20,
+     "execution_count": 18,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -477,7 +477,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -505,7 +505,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -530,7 +530,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [
     {
@@ -555,7 +555,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [
     {
@@ -582,7 +582,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
@@ -608,7 +608,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [
     {
@@ -617,7 +617,7 @@
        "'TAJ MAHAL IS BEAUTIFUL'"
       ]
      },
-     "execution_count": 12,
+     "execution_count": 24,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -635,7 +635,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 25,
    "metadata": {},
    "outputs": [
     {
@@ -644,7 +644,7 @@
        "'Bengaluru is beautiful'"
       ]
      },
-     "execution_count": 22,
+     "execution_count": 25,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -662,7 +662,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -678,7 +678,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [
     {
@@ -687,7 +687,7 @@
        "'hello'"
       ]
      },
-     "execution_count": 25,
+     "execution_count": 28,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -705,7 +705,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 29,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -714,7 +714,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 30,
    "metadata": {},
    "outputs": [
     {
@@ -723,7 +723,7 @@
        "'   ***----hello---*******     '"
       ]
      },
-     "execution_count": 27,
+     "execution_count": 30,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -741,7 +741,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 31,
    "metadata": {},
    "outputs": [
     {
@@ -767,7 +767,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 32,
    "metadata": {},
    "outputs": [
     {
@@ -807,7 +807,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 34,
    "metadata": {},
    "outputs": [
     {
@@ -833,7 +833,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 29,
+   "execution_count": 35,
    "metadata": {},
    "outputs": [
     {
@@ -852,7 +852,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 30,
+   "execution_count": 36,
    "metadata": {},
    "outputs": [
     {
@@ -877,7 +877,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 37,
    "metadata": {},
    "outputs": [
     {
@@ -901,7 +901,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": 38,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -918,7 +918,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 39,
    "metadata": {},
    "outputs": [
     {
@@ -935,6 +935,24 @@
    ]
   },
   {
+   "cell_type": "code",
+   "execution_count": 41,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{'One': 1, 'Two': 2, 'Three': 3, 'Four': 4, 'Five': 5}\n"
+     ]
+    }
+   ],
+   "source": [
+    "d3 = {names[i]:numbers[i] for i in range(len(names))}\n",
+    "print(d3)"
+   ]
+  },
+  {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -979,22 +997,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": 43,
    "metadata": {},
    "outputs": [
     {
-     "ename": "NameError",
-     "evalue": "name 'a1' is not defined",
-     "output_type": "error",
-     "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-34-ea21b6f6055b>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0ma1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mclear\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-      "\u001b[0;31mNameError\u001b[0m: name 'a1' is not defined"
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{}\n"
      ]
     }
    ],
    "source": [
+    "a1 = {1:10, 2:20}\n",
     "a1.clear()\n",
     "print(a1)"
    ]
@@ -1026,14 +1041,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 46,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "{'One': 1, 'Four': 4, 'Three': 3, 'Five': 5, 'Two': 2}\n"
+      "{'One': 1, 'Two': 2, 'Three': 3, 'Four': 4, 'Five': 5}\n"
      ]
     }
    ],
@@ -1052,7 +1067,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 36,
+   "execution_count": 47,
    "metadata": {},
    "outputs": [
     {
@@ -1061,7 +1076,7 @@
        "dict_values([1, 2, 3, 4, 5])"
       ]
      },
-     "execution_count": 36,
+     "execution_count": 47,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1079,7 +1094,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": 48,
    "metadata": {},
    "outputs": [
     {
@@ -1088,7 +1103,7 @@
        "dict_keys(['One', 'Two', 'Three', 'Four', 'Five'])"
       ]
      },
-     "execution_count": 37,
+     "execution_count": 48,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1106,7 +1121,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": 49,
    "metadata": {},
    "outputs": [
     {
@@ -1137,23 +1152,23 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 41,
+   "execution_count": 51,
    "metadata": {},
    "outputs": [
     {
-     "ename": "KeyError",
-     "evalue": "'Four'",
+     "ename": "TypeError",
+     "evalue": "pop expected at least 1 arguments, got 0",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-41-807ce32acb5c>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0ma2\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0ma1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpop\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Four'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma2\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-      "\u001b[0;31mKeyError\u001b[0m: 'Four'"
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-51-a0907f1327c5>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0ma2\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0ma1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpop\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma2\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mTypeError\u001b[0m: pop expected at least 1 arguments, got 0"
      ]
     }
    ],
    "source": [
-    "a2 = a1.pop('Four')\n",
+    "a2 = a1.pop()\n",
     "print(a1)\n",
     "print(a2)"
    ]
diff --git a/0_python/5_Control_Flow.ipynb b/0_python/5_Control_Flow.ipynb
index 2109060..7723227 100644
--- a/0_python/5_Control_Flow.ipynb
+++ b/0_python/5_Control_Flow.ipynb
@@ -25,7 +25,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -194,7 +194,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -273,7 +273,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [
     {
@@ -321,7 +321,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
diff --git a/0_python/6_Function.ipynb b/0_python/6_Function.ipynb
index ea80f1f..dc07c1c 100644
--- a/0_python/6_Function.ipynb
+++ b/0_python/6_Function.ipynb
@@ -275,7 +275,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
@@ -300,7 +300,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [
     {
@@ -321,7 +321,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -337,7 +337,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -346,7 +346,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -367,7 +367,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [
     {
@@ -385,7 +385,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
@@ -420,12 +420,12 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 33,
    "metadata": {},
    "outputs": [],
    "source": [
-    "def implicitadd(x,y=3):\n",
-    "    return x+y"
+    "def implicitadd(x,addnumber=3):\n",
+    "    return x+addnumber"
    ]
   },
   {
@@ -444,7 +444,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [
     {
@@ -453,7 +453,7 @@
        "7"
       ]
      },
-     "execution_count": 23,
+     "execution_count": 26,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -471,7 +471,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [
     {
@@ -480,7 +480,7 @@
        "8"
       ]
      },
-     "execution_count": 24,
+     "execution_count": 27,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -491,7 +491,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 34,
    "metadata": {},
    "outputs": [
     {
@@ -500,13 +500,13 @@
        "11"
       ]
      },
-     "execution_count": 20,
+     "execution_count": 34,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "implicitadd(5, y=6)"
+    "implicitadd(5, addnumber=6)"
    ]
   },
   {
@@ -525,7 +525,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 29,
+   "execution_count": 42,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -547,7 +547,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 30,
+   "execution_count": 43,
    "metadata": {},
    "outputs": [
     {
@@ -563,7 +563,7 @@
        "15"
       ]
      },
-     "execution_count": 30,
+     "execution_count": 43,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -601,14 +601,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 46,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[30, 10, 20]\n"
+      "[10, 20, 30]\n"
      ]
     },
     {
@@ -617,7 +617,7 @@
        "60"
       ]
      },
-     "execution_count": 31,
+     "execution_count": 46,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -650,7 +650,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 47,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -666,7 +666,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 48,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -732,7 +732,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 49,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -741,7 +741,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 50,
    "metadata": {},
    "outputs": [
     {
@@ -750,7 +750,7 @@
        "64"
       ]
      },
-     "execution_count": 49,
+     "execution_count": 50,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -761,7 +761,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 51,
    "metadata": {},
    "outputs": [
     {
@@ -770,7 +770,7 @@
        "(6, 8)"
       ]
      },
-     "execution_count": 27,
+     "execution_count": 51,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -782,7 +782,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 52,
    "metadata": {},
    "outputs": [
     {
@@ -791,7 +791,7 @@
        "function"
       ]
      },
-     "execution_count": 28,
+     "execution_count": 52,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -802,7 +802,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 29,
+   "execution_count": 53,
    "metadata": {},
    "outputs": [
     {
@@ -811,7 +811,7 @@
        "function"
       ]
      },
-     "execution_count": 29,
+     "execution_count": 53,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -839,7 +839,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 30,
+   "execution_count": 54,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -848,7 +848,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 56,
    "metadata": {},
    "outputs": [
     {
@@ -866,7 +866,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": 59,
    "metadata": {},
    "outputs": [
     {
@@ -891,7 +891,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": 60,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -900,7 +900,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": 61,
    "metadata": {},
    "outputs": [
     {
@@ -925,14 +925,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 39,
+   "execution_count": 62,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "<map object at 0x7f75c27604a8>\n"
+      "<map object at 0x7fd754688198>\n"
      ]
     }
    ],
@@ -973,7 +973,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 41,
+   "execution_count": 63,
    "metadata": {},
    "outputs": [
     {
@@ -998,16 +998,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 58,
+   "execution_count": 64,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<map at 0x7f72a418c780>"
+       "<map at 0x7fd7546882b0>"
       ]
      },
-     "execution_count": 58,
+     "execution_count": 64,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1025,16 +1025,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 59,
+   "execution_count": 65,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<filter at 0x7f72a4195240>"
+       "<filter at 0x7fd754688320>"
       ]
      },
-     "execution_count": 59,
+     "execution_count": 65,
      "metadata": {},
      "output_type": "execute_result"
     }
diff --git a/0_python/7_Class.ipynb b/0_python/7_Class.ipynb
index 817af0a..abab9d7 100644
--- a/0_python/7_Class.ipynb
+++ b/0_python/7_Class.ipynb
@@ -34,7 +34,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -59,7 +59,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -68,7 +68,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -77,7 +77,7 @@
        "__main__.FirstClass"
       ]
      },
-     "execution_count": 3,
+     "execution_count": 4,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -88,7 +88,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -97,7 +97,7 @@
        "type"
       ]
      },
-     "execution_count": 4,
+     "execution_count": 5,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -131,7 +131,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -139,9 +139,9 @@
      "evalue": "'FirstClass' object has no attribute 'init'",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;31m-----------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mAttributeError\u001b[0m            Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-5-d15e7b8e3d78>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0meg0\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mFirstClass\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0meg0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-6-d15e7b8e3d78>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0meg0\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mFirstClass\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0meg0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
       "\u001b[0;31mAttributeError\u001b[0m: 'FirstClass' object has no attribute 'init'"
      ]
     }
@@ -169,7 +169,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -190,7 +190,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -200,7 +200,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
@@ -228,7 +228,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 13,
    "metadata": {
     "scrolled": false
    },
@@ -265,7 +265,7 @@
        " 'class_var']"
       ]
      },
-     "execution_count": 14,
+     "execution_count": 13,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -276,7 +276,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -285,7 +285,7 @@
        "'My first class'"
       ]
      },
-     "execution_count": 10,
+     "execution_count": 14,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -303,7 +303,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -321,6 +321,7 @@
        " '__gt__',\n",
        " '__hash__',\n",
        " '__init__',\n",
+       " '__init_subclass__',\n",
        " '__le__',\n",
        " '__lt__',\n",
        " '__module__',\n",
@@ -334,11 +335,12 @@
        " '__str__',\n",
        " '__subclasshook__',\n",
        " '__weakref__',\n",
+       " 'class_var',\n",
        " 'name',\n",
        " 'symbol']"
       ]
      },
-     "execution_count": 25,
+     "execution_count": 15,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -356,7 +358,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -375,7 +377,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -385,7 +387,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [
     {
@@ -393,9 +395,9 @@
      "evalue": "'FirstClass' object has no attribute 'name'",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;31m-----------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mAttributeError\u001b[0m            Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-17-4ab7dec1c737>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31m------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0mTraceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-18-4ab7dec1c737>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
       "\u001b[0;31mAttributeError\u001b[0m: 'FirstClass' object has no attribute 'name'"
      ]
     }
@@ -414,7 +416,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -450,7 +452,7 @@
        " 's']"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 19,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -461,7 +463,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -493,7 +495,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -632,7 +634,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [
     {
@@ -652,7 +654,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [
     {
@@ -790,7 +792,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 35,
+   "execution_count": 36,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -805,7 +807,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 36,
+   "execution_count": 37,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -814,7 +816,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": 38,
    "metadata": {},
    "outputs": [
     {
@@ -831,7 +833,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": 39,
    "metadata": {},
    "outputs": [
     {
@@ -866,7 +868,7 @@
        " 'salary']"
       ]
      },
-     "execution_count": 38,
+     "execution_count": 39,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -884,7 +886,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 39,
+   "execution_count": 40,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -902,7 +904,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 40,
+   "execution_count": 41,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -911,7 +913,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 41,
+   "execution_count": 42,
    "metadata": {},
    "outputs": [
     {
@@ -930,7 +932,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 42,
+   "execution_count": 43,
    "metadata": {},
    "outputs": [
     {
@@ -966,7 +968,7 @@
        " 'salary']"
       ]
      },
-     "execution_count": 42,
+     "execution_count": 43,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -996,7 +998,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 45,
+   "execution_count": 46,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1005,7 +1007,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 47,
    "metadata": {},
    "outputs": [
     {
@@ -1041,7 +1043,7 @@
        " 'salary']"
       ]
      },
-     "execution_count": 46,
+     "execution_count": 47,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1052,7 +1054,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 48,
    "metadata": {},
    "outputs": [
     {
@@ -1078,7 +1080,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 50,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1094,7 +1096,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 51,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1103,7 +1105,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 52,
    "metadata": {},
    "outputs": [
     {
@@ -1130,7 +1132,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 53,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1147,7 +1149,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 54,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1156,7 +1158,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 53,
+   "execution_count": 55,
    "metadata": {},
    "outputs": [
     {
@@ -1181,7 +1183,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 60,
+   "execution_count": 56,
    "metadata": {},
    "outputs": [
     {
@@ -1199,7 +1201,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 61,
+   "execution_count": 57,
    "metadata": {},
    "outputs": [
     {
@@ -1224,7 +1226,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 62,
+   "execution_count": 58,
    "metadata": {},
    "outputs": [],
    "source": [
diff --git a/README.md b/README.md
index 3219f82..43d6323 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,8 @@
 
 由于**本课程需要大量的编程练习才能取得比较好的学习效果**，因此需要认真去完成[《机器学习-作业和报告》](https://gitee.com/pi-lab/machinelearning_homework)，写作业的过程可以查阅网上的资料，但是不能直接照抄，需要自己独立思考并独立写出代码。
 
+为了让大家更好的自学本课程，课程讲座的视频会陆续上传到[b站 - 机器学习](https://space.bilibili.com/421445744/channel/detail?cid=150380)，欢迎大家观看学习。
+
 ![Machine Learning Cover](images/machine_learning.png)