CODEWITHSUNDEEP
stringpython-3.xint
A.Jha
A.Jha

Reputation: 123

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.

Upvotes: 1

Views: 1761

Answers (1)

Alexander
Alexander

Reputation: 10376

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")

Upvotes: 2

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