Loops

Looping means repeating something. It is a very common programming construct. We can use it to perform repetitive actions in our programs. Let’s start with the while construct. This construct evaluates a Boolean expression in every loop, and as long as the expression returns True, the code block under while is run repeatedly. When the Boolean expression returns False, the loop terminates. Following is a simple example:

i = 0
while i < 10:
    print(i)
    i = i + 1

The output is as follows:

>>> %Run -c $EDITOR_CONTENT
0
1
2
3
4
5
6
7
8
9

Sometimes, we may wish to run the loop forever. In such cases, we can use 1 or True in place of the Boolean expression in the while construct as follows:

#while 1
while True:
    print("Processing...")

In order to exit the loop, press Ctrl + C in the shell. Following is the output:

Processing...
Processing...
Processing...
Processing...