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Python Iterative Statements
Iteration statements or loop statements allow us to execute a block of statements
repeatedly as long as the condition is true.
(Loops statements are used when we need to run same code again and again)
Type of Iteration Statements In Python 3
In Python Iteration (Loops) statements are of three types :-
1. While Loop
2. For Loop
3. Nested Loops
1. While Loop In Python
While Loop In Python is used to execute a block of statement till the 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
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Flowchart of While Loop
Python Flowchart of While Loop
Examples Of While Loop
x=0 x=1
while (x < 5): while (x <= 5):
print(x) print(―Welcome ―)
x=x+1 x=x+1
Output :- Output :-
0 Welcome
1 Welcome
2 Welcome
3 Welcome
4 Welcome
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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
—–
—–
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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
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ExampleS of For Loop
for i in range(1,5): for i in [1,2,3,4] :
print(i) print(―WELCOME ‖)
Output :- Output :-
1 WELCOME
2 WELCOME
3 WELCOME
4 WELCOME
****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 Example 2 of range() function
for i in range(5): for i in range(2,9):
print(i) print(i)
Output :- Output :-
0 2
1 3
2 4
3 5
4 6
7
8
Example 3 of range() function using step parameter Example 4 of range() function
for i in range(2,9,2): for i in range(0,-10,-2):
print(i) print(i)
Output :- Run Code
2 Output :-
4 0
6 -2
8 -4
-6
-8
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For Loop With Else In Python
The else is an optional block that can be used with for loop.Theelse block with
for loop executed only if for loops terminatesnormally.This means that the loop
did not encounter any break.
Example 1 of For Loop With Else
list=[2,3,4,6,7]
for i in range(0,len(list)):
if(list[i]==4):
print(‗list has 4‘)
else:
print(‗list does not have 4‘)
Run Code
Output :-
List has 4
list does not have 5
Example 2 of For Loop With Else
for i in range(0,len(list)):
if(list[i]==5):
print(‗5 is there in the list‘)
break
else:
print(‗list does not have 5‘)
Run Code
Output :-
list does not have 5
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NESTED loops in Python :The placing of one loop inside the body of
another loop is called nesting. When you "nest" two loops, the outer loop takes
control of the number of complete repetitions of the inner loop
1. Nested while loop
Syntax :
initialization
while(condition):
initialization of inner loop
while(conition):
------
------
Update expression of inner loop
Update expression of outer loop
Examples
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1. Nested for loop
Syntax
for iterating_var in sequence:
for iterating_var in sequence:
statements(s)
statements(s)
Example
