For Loop

for Loop is used to iterate a variable over a sequence(i.e., list or string) in the order that they appear.

Syntax:

for <variable> in <sequence>:

Output:

1

7

9

Explanation:

• Firstly, the first value will be assigned in the variable.
• Secondly all the statements in the body of the loop are executed with the same value.
• Thirdly, once step second is completed then variable is assigned the next value in the sequence and step second is repeated.
• Finally, it continues till all the values in the sequence are assigned in the variable and processed.

Program to display table of Number:

num=2
for a in range (1,6):
	print  num * a

Output:

2

4

6

8

10

Program to find sum of Natural numbers from 1 to 10.

sum=0
for n in range(1,11):
    sum+=n
print sum

Output:

55

Nested Loops

Loops defined within another Loop is called Nested Loop.

When an outer loop contains an inner loop in its body it is called Nested Looping.

Syntax:

for  <expression>:
		for <expression>:
			Body

eg:

for i in range(1,6):
    for j in range (1,i+1):
        print i,
    print

Output:

>>> 
1
2 2
3 3 3
4 4 4 4
5 5 5 5 5
>>>

Explanation:

For each value of Outer loop the whole inner loop is executed.

For each value of inner loop the Body is executed each time.

Program to print Pyramid:

for i in range (1,6):
    for j in range (5,i-1,-1):
        print "*",
    print

Output:

>>> 
* * * * *
* * * *
* * *
* *
*