Python Loops

1. Control Flow
2. Loops

Loops are basically the repetition of a certain block of code for a number of iteration or until a condition is satisfied. In python, loops are used to iterate through the iterables like List, Tuples, Dictionary, Strings, etc.

There are 2 kinds of loops in Python

• for loop

  In python, For loops are basically used to iterate over the sequences or iterables like a List, Tuple, Dictionary, Strings, etc.

  With the for loop, we can execute a set of statements, once for each item in a list, tuple, set, etc.

  Syntax

  
  for item in sequence:
      #loop-body
  

  Example 1

  
  #looping through the list
  nums=[1,2,4,53,3]
  for num in nums:
      print(num)
  

  Output

              
  1
  2
  4
  53
  3 

  Example 2

              
  for i in range(5):
      print(i)

  Output

  
  0
  1
  2
  3
  4

  Example 3

  
  languages=['python','c','c++','java','perl','ruby']
  for i in range(len(languages))
      print(i)
  

  Output

              
  python
  c
  c++
  java
  perl
  ruby

• While loop

  While loop in python is used to perform the iteration over the block of code until the certain given condition is true. While loop is used generally while we don't know the number of iterations to be iterated

  Syntax

  
  while Conditional-expression:
        #block of code
          

  Example 1

  
  #program to print 1 to 10 numbers
  num=1
  while(num<10):
      print(num)
      num+=1
  

  Output

  
  1
  2
  3
  4
  5
  6
  7
  8
  9 

  Example 2

  
  #program to find out factorial of any number
  num=int(input("Enter number: "))
  factorial=1
  i=1
  while(i<=num):
      factorial*=i
      i=i+1
      print("Factorial of {} is {}.".format(num,factorial})
  

  Output

  
  Enter number: 5
  Factorial of 5 is 120.

The range() function

The range() function is a very useful function that is used to generate a sequence of numbers. For example, range(5) will generate 0 to 5. Also, we can pass parameters to this function to make it more useful and flexible. The syntax would be range(start,end,step-size). Here, range(1,10,2) will produce all the odd numbers between 1 to 10.

Example

>>>print(list(range(10))
   [1,2,3,4,5,6,7,8,9]
>>>print(list(range(2,7))
   [2,3,4,5,6]
>>>print(list(range(2,10,2))
   [2,4,6,8,10]