Python For Loop

Introduction

 

In this article, we will discuss Python's for a loop. Same as while loop, for loop, also control flow statement. In Python, for loop is used when we want to iterate over a sequence.

 

Syntax

for IterationalVariable in sequence:
        Body of the loop

In Python, for loop works like C# foreach loop.

 

For loop with list

 

The following example explains how can you iterate a list using for loop.

 

Example

list=['C','C++','Java','C#']
print("This is our list ",list)
i=1
for val in list:
    print("List Item",i,"is",val)
    i=i+1

Output

 

 

For loop with tuple

 

The following example explains how can you iterate tuple using for loop.

 

Example

tuple=('C','C++','Java','C#','Python')
print("This is our Tuple ",tuple)
i=1
for val in tuple:
    print("Tuple Item",i,"is",val)
    i=i+1

Output

 

 

For loop with string

 

The following example explains how can you iterate string using for loop.

 

Example

string="C-Sharp Corner"
for val in string:
    print(val)

Output

 

 

Range Function

 

Sometimes we need to iterate loop in a given range and we cannot create a sequence. For example, if you want to print a number from one to 1000, so will you create a sequence or list from 1 to 1000? Of course, you cannot go like this. So in Python, we have a range function, in which we will decide range inside the function.

 

Syntax of range function

range([start],end,[step])

          In Python range function has 3 arguments In which two are optional, which are the following:

• start- This is an optional argument. This argument decides from where you want to start your loop. If you do not provide this value then its value will be zero(0) by default.
    
• end- This argument decides the end of the loop.
    
• step- How much you want to increment after one iteration. This is also an optional argument. So if you do not give this argument then it will increment by 1 step. 

Example 1

for val in range(11):
    print(val)

In the above example range contains only one parameter so that it will be the end parameter and start and step will be set with its default value, so start will be 0 and step will be 1 and the value of end is 11.

 

Output 

 

Example 2

for val in range(1,11):
    print(val)

The above example range contains two parameters so that it will be the start and end parameter and the step will be set with its default value. So in the above example. start=1,end=11 and step=1(default).

 

Output

 

 

Example 3

for val in range(1,11,2):
    print(val)

In the above example start=1 end=11 and step=2.

 

Output

 

 

For loop with else condition

 

Same as while loop you can also use for loop with else condition in python. For loop works the same as normal for loop but whenever for loop condition will be false it's else part will execute.

 

Note

 

else part will only execute when for loop condition will be false. If for loop will be terminated by break statement then for loop's else part never executes.

 

Example

#program to check
#weather the given number is
#prime number or not
num = int(input("Enter a Number : "))
for i in range(2,num):
    if(num%i==0):
        print("%d is not a prime number..."%num)
        break
else:
    print("%d is a prime number..."%num)

Output 

 

 

Nested Loop

 

A nested loop means a loop inside the loop. In python, you can create loop inside a loop. 

 

Example 1

str="";
for Row in range(0,7):
    for Col in range(0,7):
        if (((Col == 1 or Col == 5) and Row != 0) or ((Row == 0 or Row == 3) and (Col > 1 and Col < 5))):
            str=str+"*"
        else:
            str=str+" "
    str=str+"\n"
print(str);

Output

 

 

Example 2

str="";
for Row in range(0,7):
    for Col in range(0,7):
        if (Col == 1 or ((Row == 0 or Row == 3 or Row == 6) and (Col < 5 and Col > 1)) or (Col == 5 and (Row != 0 and Row != 3 and Row != 6)))  :
            str=str+"*"
        else:
            str=str+" "
    str=str+"\n"
print(str);

Output

 

 

Example 3

row=15
col=18
str=""
for i in range(1,row+1):
    if((i<=3)or(i>=7 and i<=9)or(i>=13 and i<=15)):
        for j in range(1,col):
            str=str+"*"
        str=str+"\n"
    elif(i>=4 and i<=6):
        for j in range(1,5):
            str=str+"*"
        str=str+"\n"
    else:
        for j in range(1,14):
            str=str+" "
        for j in range(1,5):
            str=str+"*"
        str=str+"\n"
print(str)

Output

 

 

Summary

 

In this article, we learned about Python For Loop and how to use For loop in programming.