Python Do While Loops

In Python, there is no construct defined for do while loop. Python loops only include for loop and while loop but we can modify the while loop to work as do while as in any other languages such as C++ and Java.

In Python, we can simulate the behavior of a do-while loop using a while loop with a condition that is initially True and then break out of the loop when the desired condition is met.

Do while loop

Do while loop is a type of control looping statement that can run any statement until the condition statement becomes false specified in the loop. In do while loop the statement runs at least once no matter whether the condition is false or true.

Syntax of do while loop:

do{
    // statement or 
    // set of statements
}
while(condition)

Example of do while loop in C++

In this example, we are going to print multiple of 2 using the do while loop. So, that we can understand the working of do while loop.

#include <iostream>
using namespace std;

int main() {

    int i=0;
      // Defining do while loop 
      // to write multiple of 2
      do{
      i++;
      cout<<"2 x "<<i<<"="<<2*i<<endl;
    }while(i<5);
  
    return 0;
}

Output: In the below output we can clearly see that program also prints "2 x 5=10" even though 5 is not less than 5.

2 x 1=2
2 x 2=4
2 x 3=6
2 x 4=8
2 x 5=10

Examples of do while loop in Python : 

Example 1 :

In this example, we are going to implement the do-while loop in Python using the while loop and if statement in Python and comparing the while loop with the do-while loop in python.

# defining list of strings
list1 = ["geeksforgeeks", "C++",
         "Java", "Python", "C", "MachineLearning"]

# initialises a variable
i = 0

print("Printing list items\
 using while loop")
size = len(list1)
# Implement while loop to print list items
while(i < size):
    print(list1[i])
    i = i+1

i = 0

print("Printing list items\
 using do while loop")

# Implement do while loop to print list items
while(True):
    print(list1[i])
    i = i+1
    if(i < size and len(list1[i]) < 10):
        continue
    else:
        break

Output: The while is printing the items in the list. The Do while loop is having two conditions for terminating.

The pointer of the list reached its last+1 position and any element of the list index having length >=10. In this code output, we can see that-

The Do While loop is terminated, because the condition len(list1[5])<10 is not fulfilling.

Printing list items using while loop
geeksforgeeks
C++
Java
Python
C
MachineLearning
Printing list items using do while loop
geeksforgeeks
C++
Java
Python
C

Example 2:

total = 0
# loop will run at least once
while True:
    # ask the user to enter a number
    num = int(input("Enter a number (or 0 to exit): "))

    # exit the loop if the user enters 0
    if num == 0:
        break
    total += num

# print the total
print("Total:", total)

Output: In this code, we can see that a while loop is running and accepting the input from the user and adding it. When 0 is entered then it will break out of the loop and print the sum of all numbers which adds input by the user before 0.

Enter a number (or 0 to exit): 1
Enter a number (or 0 to exit): 3
Enter a number (or 0 to exit): 2
Enter a number (or 0 to exit): 0
Total: 6