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Python while Loop

Video link: https://youtu.be/5AOfDuV6X30

In this video, we learned about loops to repeat certain blocks of code, specifically using the while loop.

Programs in the Video

Python while loop

Looping is a fundamental concept in all programming languages, not just Python. They are used to repeat a block of code multiple times as per our requirement. One such type of loop is the while loop.

The syntax of the while loop in Python is:

while test_condition:
    statement(s)

Here, the statements inside the while loop are executed for as long as test_condition evaluates to True.

Example: Using while Loops

count = 0

while count < 5:
    print("I am inside a loop.")
    print("Looping is interesting.")

Output

I am inside a loop.
Looping is interesting.
...

Here, the test condition is never False, so the loop runs forever until the system's memory runs out.

Generally, we want programs that terminate at one point. For that, we can alter the value of count at every iteration like:

count = 0

while count < 5:
    print("I am inside a Loop.")
    print("Looping is interesting.")
    count = count + 1

Output

I am inside a loop.
Looping is interesting.
I am inside a loop.
Looping is interesting.
I am inside a loop.
Looping is interesting.
I am inside a loop.
Looping is interesting.
I am inside a loop.
Looping is interesting.

To understand what is going on let's print the value of count:

count = 0

while count < 5:
    print(count)
    count = count + 1

Output

0
1
2
3
4

Here, the block of code executes only 5 times as count goes from 0 to 4. At count = 5 the test condition is False and the loop terminates.

Programming Task 1

Can you guess the output of this program?

count = 5

while count <= 10:
    print(count)
    count = count + 1

Output

5
6
7
8
9
10

Example: Multiplication Table

number = int(input("Enter a number: "))

count = 1

while count <= 10:
    product = number * count
    print(product)
    count = count + 1

Output

Enter a number: 6
6
12
18
24
30
36
42
48
54
60

To make it more readable, we can print number, count, and product adjacently using the following code:

number = int(input("Enter a number: "))

count = 1

while count <= 10:
    product = number * count
    print(number, "x", count, "=", product)
    count = count + 1

Output

Enter a number: 6
6 * 1 = 6
6 * 2 = 12
6 * 3 = 18
6 * 4 = 24
6 * 5 = 30
6 * 6 = 36
6 * 7 = 42
6 * 8 = 48
6 * 9 = 54
6 * 10 = 60

Programming Task 2

Can you modify our multiplication table program so that we get a multiplication table from 10 to 1 instead of 1 to 10.

number = int(input("Enter a number: "))

count = 10

while count >= 1:
    product = number * count
    print(number, "x", count, "=", product)
    count = count - 1

Output

Enter a number: 6
6 x 10 = 60
6 x 9 = 54
6 x 8 = 48
6 x 7 = 42
6 x 6 = 36
6 x 5 = 30
6 x 4 = 24
6 x 3 = 18
6 x 2 = 12
6 x 1 = 6