Iteration statements or loop statements allow us to execute a block of statements as long as the condition is true.
Loops statements are used when we need to run same code again and again, each time with a different value.
Type of Iteration Statements In Python 3
In Python Iteration (Loops) statements are of three types :-
1. While Loop
2. For Loop
1. While Loop In Python
While Loop In Python is used to execute a block of statement as long as a given condition is true. And when the condition is false, the control will come out of the loop.
The condition is checked every time at the beginning of the loop.
While Loop Syntax
while (condition):
statements
Flowchart of While Loop
Python Flowchart of While Loop
Example Of While Loop
x = 0
while (x < 5):
print(x)
x = x + 1
Output :-
0
1
2
3
4
While Loop With Else In Python
The else part is executed if the condition in the while loop becomes False.
Syntax of While Loop With Else
while (condition):
loop statements
else:
else statements
Example of While Loop With Else
x = 1
while (x < 5):
print(‘inside while loop value of x is ‘,x)
x = x + 1
else:
print(‘inside else value of x is ‘, x)
Output :-
inside while loop
value of x is 1
inside while loop value of x is 2
inside while loop value of x is 3
inside while loop value of x is 4
inside else value of x is 5
Infinite While Loop In Python
A Infinite loop is a loop in which condition always remain True.
Example of Infinite While Loop
x = 1
while (x == 1):
print(‘hello’)
Output :-
hello
hello
hello
—–
—–
2. For Loop In Python
For loop in Python is used to iterate over items of any sequence, such as a list or a string.
For Loop Syntax
for val in sequence:
statements
Flowchart of For Loop
Python Flowchart of For Loop
Example of For Loop
for i in range(1,5):
print(i)
Output :-
1
2
3
4
The range() Function In Python
The range() function is a built-in that is used to iterate over a sequence of numbers.
Syntax Of range() Function
range(start, stop[, step])
The range() Function Parameters
start: Starting number of the sequence.
stop: Generate numbers up to, but not including this number.
step(Optional): Determines the increment between each numbers in the
sequence.
Example 1 of range() function
for i in range(5):
print(i)
Output :-
0
1
2
3
4
Example 2 of range() function
for i in range(2,9):
print(i)
Output :-
2
3
4
5
6
7
8
Example 3 of range() function using step parameter
for i in range(2,9,2):
print(i)
Output :-
2
4
6
8
Example 4 of range() function
for i in range(0,-10,-2):
print(i)
Run Code
Output :-
0
-2
-4
-6
-8
For Loop With Else In Python
The else is an optional block that can be used with for loop.The else block with for loop executed only if for loops terminates normally.This means that the loop did not encounter any break.
Example of For Loop With Else
list=[2,3,4,6,7]
for i in range(0,len(list)):
if(list[i]==5):
print(‘list has 5’)
break
else:
print(‘list does not have 5’)
Run Code
Output :-
list does not have 5
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