Learn Python – Python for loop- Basic and advance

The for loop in Python is used to iterate the statements or a part of the application countless times. It is frequently used to traverse the records buildings like list, tuple, or dictionary.

The syntax of for loop in python is given below.

for iterating_var in sequence:    
    statement(s)    

The for loop flowchart

For loop Using Sequence

Example-1: Iterating string using for loop

str = "Python"  
for i in str:  
    print(i)  

Output:

P
y
t
h
o
n

Example- 2: Program to print the table of the given quantity .

list = [1,2,3,4,5,6,7,8,9,10]  
n = 5  
for i in list:  
    c = n*i  
    print(c)  

Output:

5
10
15
20
25
30
35
40
45
50s

Example-4: Program to print the sum of the given list.

list = [10,30,23,43,65,12]  
sum = 0  
for i in list:  
    sum = sum+i  
print("The sum is:",sum)  

Output:

The sum is: 183

For loop Using range() function

The range() function

The range() feature is used to generate the sequence of the numbers. If we ignore the range(10), it will generate the numbers from zero to 9. The syntax of the range() function is given below.

Syntax:

range(start,stop,step size)  

The start represents the beginning of the iteration.

The stop represents that the loop will iterate till stop-1. The range(1,5) will generate numbers 1 to 4 iterations. It is optional.

The step size is used to skip the specific numbers from the iteration. It is optional to use. By default, the step size is 1. It is optional.

Consider the following examples:

Example-1: Program to print numbers in sequence.

for i in range(10):  
    print(i,end = ' ')  

Output:

0 1 2 3 4 5 6 7 8 9 

Example – 2: Program to print table of given number.

n = int(input("Enter the number "))  
for i in range(1,11):  
    c = n*i  
    print(n,"*",i,"=",c)  

Output:

Enter the number 10
10 * 1 = 10
10 * 2 = 20
10 * 3 = 30
10 * 4 = 40
10 * 5 = 50
10 * 6 = 60
10 * 7 = 70
10 * 8 = 80
10 * 9 = 90
10 * 10 = 100

Example-3: Program to print even quantity using step size in range().

n = int(input("Enter the number "))  
for i in range(2,n,2):  
    print(i)  

Output:

Enter the number 20
2
4
6
8
10
12
14
16
18

We can additionally use the range() feature with sequence of numbers. The len() function is blended with range() characteristic which iterate via a sequence the use of indexing. Consider the following example.

list = ['Peter','Joseph','Ricky','Devansh']  
for i in range(len(list)):  
    print("Hello",list[i])  

Output:

Hello Peter
Hello Joseph
Hello Ricky
Hello Devansh

Nested for loop in python

Python permits us to nest any number of for loops inside a for loop. The inner loop is achieved n number of instances for every new release of the outer loop. The syntax is given below.

Syntax

for iterating_var1 in sequence:  #outer loop  
    for iterating_var2 in sequence:  #inner loop  
        #block of statements     
#Other statements    

Example- 1: Nested for loop

# User input for number of rows  
rows = int(input("Enter the rows:"))  
# Outer loop will print number of rows  
for i in range(0,rows+1):  
# Inner loop will print number of Astrisk  
    for j in range(i):  
        print("*",end = '')  
    print()  

Output:

Enter the rows:5
*
**
***
****
*****

Example-2: Program to number pyramid.

rows = int(input("Enter the rows"))  
for i in range(0,rows+1):  
    for j in range(i):  
        print(i,end = '')  
    print()  

Output:

1
22
333
4444
55555

Using else statement with for loop

Unlike other languages like C, C++, or Java, Python permits us to use the else declaration with the for loop which can be accomplished only when all the iterations are exhausted. Here, we should be aware that if the loop incorporates any of the break declaration then the else statement will not be executed.

Example 1

for i in range(0,5):    
    print(i)    
else:  
    print("for loop completely exhausted, since there is no break.")  

Output:

0
1
2
3
4
for loop completely exhausted, since there is no break.

The for loop totally exhausted, on the grounds that there is no break.

Example 2

for i in range(0,5):    
    print(i)    
    break;    
else:print("for loop is exhausted");    
print("The loop is broken due to break statement...came out of the loop")    

In the above example, the loop is damaged due to the destroy statement; therefore, the else statement will no longer be executed. The announcement existing instantaneous next to else block will be executed.

Output:

0

The loop is broken due to the wreck statement…came out of the loop. We will study more about the damage assertion in subsequent tutorial.