While Loops

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

Syntax

while expression:
    statement(s) / Body of the while loop

Example:

num = 0
while num <= 7:
    print(num)
    num = num + 1 (This is same: num += 1)

To increment the value of the “num” variable is very important because, without incrementing the value of num, our Loop will never end and will go to the infinity

One-Line while loop

Example:

num = 0
while num < 7: print(num); num += 1 
# Or 
while num < 7: print(num); num = num + 1

In both cases (While loop and one-line while loop) the output will be the same

Output:

0
1
2
3
4
5
6
7

The Infinite Loop

A loop becomes infinite loop if a condition never becomes FALSE. So there is no guarantee that the loop will stop unless we write the necessary code to make the condition False at some point during the execution of the loop. This results in a loop that never ends.

Example:

num = 2
while num == 2:
    print("This is Infinite Loop")

Output:

This is Infinite Loop
This is Infinite Loop
This is Infinite Loop
This is Infinite Loop
This is Infinite Loop
This is Infinite Loop

You need to use CTRL+C to exit the program.

The condition num = 2 is always True so the loop never stops.If you want different result, you need to write a condition.

Example:

num = 2
while num == 2:
    print("Infinite")
    num += 1

# Output:
Infinite

Using else Statement with While Loop

If the else statement is used with a while loop, the else statement is executed when the condition becomes false.

The following example illustrates the combination of an else statement with a while statement that prints a number as long as it is less than 5, otherwise else statement gets executed.

Example:

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

# output:
1
2
3
4
5
i is no longer less than 6

Loop control statements - While loop

Statements break and continue

BREAK is used to stop the loop even if the while condition is true while with CONTINUE we can stop the current iteration, and continue with the next. Here are some examples:

Continue

It is used to exit the Loop.

Example:

num = 0
while num <7:
    num += 1
    if num == 5:
        continue
    print(num)

output - The continue statement is executed and as a result the number 5 is skipped from the count.

1
2
3
4
6
7

Break

num = 0
while num < 5:
    num += 1
    if num == 4:
        break
    print(num)

Output - The break instruction is executed and as a result the program stops executing with the number four.

1
2
3

Pass

It is not considered as a declaration of operation. It is more like a comment but it is executed as a valid statement although it is completely ignored. It is generally used to indicate nullity.

Example:

num = 0
while num < 7:
    num += 1
    if num == 5:
        pass
    print(num)