Why would I use int( input().strip() ) instead of just int( input() ) in Python?

Question

If I want to take a number as input, would I also need the .strip() method? Like this:

n = int(input().strip())

Instead of just coding:

n = int(input())

I know .strip() returns a copy of the string in which all chars have been stripped from the beginning and the end of the string. But I wonder why / if it is necessary.

Answer 1

It isn't necessary when you cast it to an integer with int because int already handles (ignores) leading and trailing whitespaces*:

>>> int('1 ')
1
>>> int(' 1')
1
>>> int(' 1\n\t')  # also handles other spaces like newlines or tabs
1

It's mostly important to strip the whitespaces if you use sys.stdin.readline (which contains a trailing newline character) and you don't know if the function that uses that value can handle additional whitespaces.

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* Just FYI: The types float, complex, fractions.Fraction, and decimal.Decimal also ignore leading and trailing whitespaces so you don't need to strip the strings if you use any of those.