Have a print method in a print statement in python

Question

I have the following piece of code in Python which tries to put a function that prints something in a print statement.

def my_print(num: int) -> None:
    for i in range(num):
        print(i, end=' ')

if __name__ == '__main__':
    print('When num is 5 :', my_print(5))

I expect to get something like

When num is 5 : 0 1 2 3 4

But I actually get

0 1 2 3 4 When num is 5 : None

Could someone please explain the logic behind the print function in this case and where that None comes from at the end? Thanks.

Answer 1

Try this:

def my_print(num: int) -> None:
    for i in range(num):
        print(i, end=' ')

if __name__ == '__main__':
    print('When num is 5 :', end=" ")
    my_print(5)

The None was printing because your my_print() function would return a None to the calling position.

Answer 2

You can try list comprehension as an alternative

def my_print(num: int) -> str:
    return ' '.join(map(str, [i for i in range(num)]))

if __name__ == '__main__':
    print(f'When num is 5 : {my_print(5)}')

output

When num is 5 : 0 1 2 3 4