Updated for loop

Author: ankurdhamija83

2. Flow_control/.ipynb_checkpoints/2. For_Loop-checkpoint.ipynb

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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 1. For Loop\n",
+    "The for loop in Python is used to iterate over a sequence (list, tuple, string) or other iterable objects. \n",
+    "\n",
+    "**Syntax of for loop**<br>\n",
+    "for val in sequence:<br>\n",
+    "&emsp;loop body\n",
+    "\n",
+    "Here, `val` is the variable that takes the value of the item inside the sequence on each iteration.\n",
+    "`Loop continues` until we reach the `last item` in the sequence. The body of for loop is separated from the rest of the code using indentation."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The sum is 48\n"
+     ]
+    }
+   ],
+   "source": [
+    "#Example of for Loop\n",
+    "#Program to find the sum of all numbers stored in a list\n",
+    "\n",
+    "# List of numbers\n",
+    "numbers = [6, 5, 3, 8, 4, 2, 5, 4, 11]\n",
+    "\n",
+    "# variable to store the sum\n",
+    "sum = 0\n",
+    "\n",
+    "# iterate over the list\n",
+    "for val in numbers:\n",
+    "    sum = sum+val\n",
+    "\n",
+    "print(\"The sum is\", sum)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 2. Range() function\n",
+    "- We can generate a sequence of numbers using `range()` function. `range(10)` will generate numbers from 0 to 9 (10 numbers).\n",
+    "- We can also define the start, stop and step size as `range(start, stop,step_size)`. step_size defaults to 1 if not provided.\n",
+    "- The `range` object is \"lazy\" in a sense because it doesn't generate every number that it \"contains\" when we create it. However, it is not an iterator since it supports `in`, `len` and `__getitem__` operations.\n",
+    "- This function does not store all the values in memory; it would be inefficient. So it remembers the start, stop, step size and generates the next number on the go.\n",
+    "- To force this function to output all the items, we can use the function `list()`.\n",
+    "- The following example will clarify this."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "range(0, 10)\n",
+      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
+      "[2, 3, 4, 5, 6, 7]\n",
+      "[2, 5, 8, 11, 14, 17]\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(range(10))\n",
+    "\n",
+    "print(list(range(10)))\n",
+    "\n",
+    "print(list(range(2, 8)))\n",
+    "\n",
+    "print(list(range(2, 20, 3)))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 3. Using range() with for loops\n",
+    "We can use the range() function in for loops to iterate through a sequence of numbers. It can be combined with the len() function to iterate through a sequence using indexing. Here is an example."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "I like pop\n",
+      "I like rock\n",
+      "I like jazz\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Program to iterate through a list using indexing\n",
+    "\n",
+    "genre = ['pop', 'rock', 'jazz']\n",
+    "\n",
+    "# iterate over the list using index\n",
+    "for i in range(len(genre)):\n",
+    "    print(\"I like\", genre[i])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 4. Combining loops with if/else\n",
+    "A `for` loop can have an optional `else` block as well. The `else` part is executed if the items in the sequence used in for loop exhausts.\n",
+    "\n",
+    "The `break` keyword can be used to stop a for loop. In such cases, the else part is ignored.\n",
+    "\n",
+    "Hence, a for loop's else part runs if no break occurs.\n",
+    "\n",
+    "Here is an example to illustrate this."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "1\n",
+      "5\n",
+      "No items left.\n"
+     ]
+    }
+   ],
+   "source": [
+    "digits = [0, 1, 5]\n",
+    "\n",
+    "for i in digits:\n",
+    "    print(i)\n",
+    "else:\n",
+    "    print(\"No items left.\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "No entry with that name found.\n"
+     ]
+    }
+   ],
+   "source": [
+    "# program to display student's marks from record\n",
+    "student_name = 'Soyuj'\n",
+    "\n",
+    "marks = {'James': 90, 'Jules': 55, 'Arthur': 77}\n",
+    "\n",
+    "for student in marks:\n",
+    "    if student == student_name:\n",
+    "        print(marks[student])\n",
+    "        break\n",
+    "else:\n",
+    "    print('No entry with that name found.')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
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