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stringpython-3.xint

How to check if the input string is an integer

if input()==int():
    print('mission successful!')
else:
    print('mission failed!')

for above code the problem is, that it never results in mission successful even though my input is integer.

I have just started learning python.

Solution

  • To check if the input string is numeric, you can use this:

    s = input()
if s.isnumeric() or (s.startswith('-') and s[1:].isdigit()):
    print('mission successful!')
else:
    print('mission failed!')

    In Python, checking if a string equals a number will always return False. In order to compare strings and numbers, it helps to either convert the string to a number or the number to a string first. For example:

    >>> "1" == 1
False
>>> int("1") == 1
True

    or

    >>> 1 == "1"
False
>>> str(1) == "1"
True

    If a string can not be converted to a number with int, a ValueError will be thrown. You can catch it like this:

    try:
    int("asdf")
except ValueError:
    print("asdf is not an integer")