Python while Loop

Python Loops

Python has two primitive loop commands:

The while Loop

With the while loop we can execute a set of statements as long as a condition is true.

Example

Print i as long as i is less than 6:

 
i = 1

while i < 6:

  print(i)

  i += 1

Note: remember to increment i, or else the loop will continue forever.

The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, i, which we set to 1.

The break Statement

With the break statement we can stop the loop even if the while condition is true:

Example

Exit the loop when i is 3:

 
i = 1

while i < 6:

  print(i)

    if i == 3:
    break
  i += 1

The continue Statement

With the continue statement we can stop the current iteration, and continue with the next:

Example

Continue to the next iteration if i is 3:

 
i = 0

while i < 6:

    i += 1

  if i == 3:
    continue
  print(i)

The else Statement

With the else statement we can run a block of code once when the condition no longer is true:

Example

Print a message once the condition is false:

 
i = 1

while i < 6:

  print(i)

  i += 1
else:
  print("i is no longer less than 6")

Test Yourself With Exercises

Exercise:

Print i as long as i is less than 6.

Python While Loop

In Python, While Loops is used to execute a block of statements repeatedly until a given condition is satisfied. And when the condition becomes false, the line immediately after the loop in the program is executed. While loop falls under the category of indefinite iteration. Indefinite iteration means that the number of times the loop is executed isn’t specified explicitly in advance.

Syntax:

 
while expression:
    statement(s)

Statements represent all the statements indented by the same number of character spaces after a programming construct are considered to be part of a single block of code. Python uses indentation as its method of grouping statements. When a while loop is executed, expr is first evaluated in a Boolean context and if it is true, the loop body is executed. Then the expr is checked again, if it is still true then the body is executed again and this continues until the expression becomes false.

Example:

 # Python program to illustrate 
# while loop 
count =0
while(count < 3):     
    count =count +1
    print("Hello Geek") 
  
print()
  
# checks if list still
# contains any element 
a =[1, 2, 3, 4]
whilea:
    print(a.pop())

Output:

 
Hello Geek
Hello Geek
Hello Geek

4
3
2
1

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