Use for loop with the range() function

The range() function in Python is often used in for statements to define the number of loop iterations. This built-in function creates lists containing arithmetic progressions. The syntax of the range() function is:

range(start, stop [, step])

The start argument is the starting number. The stop argument is the last number (which is not included). The step argument is optional and defines the difference between each number in the sequence.

If the step argument is omitted, it defaults to 1. If the start argument is omitted, it defaults to 0. Note that all arguments have to be integers.


Here is an example. Let’s say that we want to loop through a for loop 10 times. We can use the range(1, 11) function inside a for statement to do that:

for i in range(1, 11):
    print ('This is the', i, 'iteration.')

When run, the code above gives the following output:

This is the 1 iteration.
This is the 2 iteration.
This is the 3 iteration.
This is the 4 iteration.
This is the 5 iteration.
This is the 6 iteration.
This is the 7 iteration.
This is the 8 iteration.
This is the 9 iteration.
This is the 10 iteration.

Notice that we didn’t specify the step argument in the example above, so it defaulted to 1. Also, notice that the last number is 10, and not 11. This is because the number defined as the stop argument isn’t included in the range.

Here is another example, this time with the step argument defined:

for i in range(1, 11, 2):
    print ('This will print only odd numbers:', i)

The output:

This will print only odd numbers: 1
This will print only odd numbers: 3
This will print only odd numbers: 5
This will print only odd numbers: 7
This will print only odd numbers: 9

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