Looping Statements and Control Statements in Python

LOOPING STATEMENTS AND
CONTROL STATEMENTS IN PYTHON
Ms.C.PRIYANKA
AP/CSE
KIT-KALAIGNARKARUNANIDHI INSTITUTE OF
TECHNOLOGY ,
COIMBATORE

While loop statement in Python is used to
repeatedly executes set of statement as long
as a given condition is true.
 In while loop, test expression is checked first.

The body of the loop is entered only if the
test_expression is True. After one iteration, the
test expression is checked again.
 This process continues until the
test_expression evaluates to False.
In Python, the body of the while loop is
determined through indentation.
The statements inside the while starts with
indentation and the first unindented line marks
the end.

1. Program to find sum of n numbers:
2. Program to find factorial of a number
3. Program to find sum of digits of a number:
4. Program to Reverse the given number:
5. Program to find number is Armstrong
number or not
6. Program to check the number is palindrome
or not

n=eval(input("enter n"))
i=1
sum=0
while(i<=n):
sum=sum+i
i=i+1
print(sum)
enter n
10
55
Factorial of a numbers: output
n=int(input("enter n"))
i=1
fact=1
while(i<=n):
fact=fact*i
i=i+1
print(fact)
enter n
5
120
Sum of digits of anumber: output
n= int (input("enter anumber"))
sum=0
while(n>0):
a=n%10
sum=sum+a
n=n//10
print(sum)
enter a number
123
6

Reverse the given number: output
n= int (input("enter a number")) sum=0
while(n>0):
a=n%10
sum=sum*10+a
n=n//10
print(sum)
enter a number 123
321
Armstrong number ornot output
n=eval(input("enter a number")) enter a number153
org=n The given number is Armstrong number
sum=0
while(n>0):
a=n%10
sum=sum+a*a*a
n=n//10
if(sum==org):
print("The given number is Armstrong
number")
else:
print("The given number is not
Armstrong number")

Palindrome or not output
n=eval(input("enter a number")) enter a number121
org=n The given no is palindrome
sum=0
while(n>0):
a=n%10
sum=sum*10+a
n=n //10
if(sum==org):
print("The given no is palindrome")
else:
print("The given no is not palindrome")

for in range:
 We can generate a sequence of numbers using range()
function. range(10) will generate numbers from 0 to 9 (10
numbers).
 In range function have to define the start, stop and step size
 as range(start,stop,step size). step size defaults to 1 if not
provided.
Syntax:

For in sequence
The for loop in Python is used to iterate over a
sequence (list, tuple, string).
Iterating over a sequence is called traversal.
Loop continues until we reach the last
element in the sequence.
The body of for loop is separated from the rest
of the code using indentation

Sequence can be a list, strings or
tuples:
S.No Sequences Example Output
1. For loop in string for i in "Ramu":
print(i)
R
A
M
U
2. For loop in list for i in [2,3,5,6,9]: print(i)
2
3
5
6
9
3. For loop in tuple
for i in (2,3,1): print(i) 2
3
1

1. print nos divisible by 5 not by 10
2. Program to print fibonacci series
3. Program to find factors of a given number
4. check the given number is perfect number or
not
5. check the no is prime or not
6. Print first n prime numbers
7. Program to print prime numbers in range

Fibonacci series output
a=0
b=1
n=int(input("Enter the number of terms: "))
print("Fibonacci Series: ")
print(a,b)
for i in range(1,n,1):
c=a+b
print(c)
a=b
b=c
Enter the number of terms: 6
Fibonacci Series:
0 1
1
2
3
5
8
find factors of a number Output
n=int(input("enter a number:"))
for i in range(1,n+1,1):
if(n%i==0):
print(i)
enter a number:10 1
2
5
10

Check The No Is Prime Or Not Output
n=int(input("enter a number"))
for i in range(2,n):
if(n%i==0):
print("The num is not a prime") break
else:
print("The num is a prime number.")
enter a no:7
The num is a prime number.
Check A Number Is Perfect Number Or Not Output
n=int(input("enter a number:")) sum=0
for i in range(1,n,1):
if(n%i==0):
sum=sum+i if(sum==n):
print("the number is perfect number")
else:
print("the number is not perfect number")
enter a number:6
the number is perfect number

• Python programming language allows using
one loop inside another loop.
• We can use one or more loop inside any
another while, for or do...while loop.

else in for loop:
• If else statement is used in for loop, the else
statement is executed when the loop has
reached the limit.
• The statements inside for loop and statements
inside else will also execute

example output
for i in range(1,6):
print(i)
else:
print("the number greater than6")
1
2
3
4
5 the number greater than 6

else in while loop:
• If else statement is used within while loop ,
the else part will be executed when the
condition become false.
• The statements inside for loop and statements
inside else will also execute

Program output
i=1
while(i<=5
):
print
(i)
i=i+
1
else:
print("the number greater than5")
1
2
3
4
5
the number greater than 5

Break statements can alter the flow of a loop.
It terminates the current loop and executes
the remaining statement outside the loop.
If the loop has else statement, that will also
gets terminated and come out of the loop
completely.

Flowchart
example Output
for i in "welcome":
if(i=="c"):
break
print(i)
w
e
l

• It terminates the current iteration and transfer
the control to the next iteration in the loop.
Syntax:
Continue

Example: Output
for i in
"welcome":
if(i=="c"):
continue
print(i)
w
e
l
o
m
e

It is used when a statement is required
syntactically but you don’t want any code to
execute.
It is a null statement, nothing happens when it is
executed.
Syntax:
pass
break

Example Output
for i in “welcome”:
if (i == “c”):
pass
print(i)
w
e
l
c
o
m
e

Break Continue
It terminates the current loop and
executes the remaining statement outside
the loop.
It terminates the current iteration and
transfer the control to the next iteration
in
the loop.
syntax:
break
syntax:
continue
for i in"welcome":
if(i=="c"):
break
print(i)
for i in
"welcome":
if(i=="c"):
continue
print(i)
w
e l
w
e
l
m
e

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