How can I tell if a string in python is either an int or float using if condition?

Question

I am getting different strings, some are numbers, for example: "1", "afd76", "dddd", "521129" and "0.1423105". I need to check if they are valid numbers before I can continue. In the above examples all are numbers apart from "afd76" and "dddd".

isdigit and isnumeric wont do because they can only verify if the string is an int, for example:

"3".isdigit() is true but "3.0".isdigit() is false
"3".isnumeric() is true but "3.0".isnumeric() is false

Is there any elegant way to do this check other than force casting and deciding what to do depending on the exception?

I'd probably use [**`ast.literal_eval`**](https://docs.python.org/3/library/ast.html#ast.literal_eval). — Peter Wood, Jul 26 '22 at 20:06
The most effective way is with a try except: `try: n=float(s); except ValueError: n=0` — joanis, Jul 26 '22 at 20:07
https://stackoverflow.com/questions/354038/how-do-i-check-if-a-string-is-a-number-float — Shavk with a Hoon, Jul 26 '22 at 20:08

PApostol · Answer 1 · 2022-07-26T20:17:38.247

3

You can try casting the string into float:

def is_number(num):
    try:
        float(num)
        return True
    except ValueError:
        return False

Examples:

>>> is_number('123')
True
>>> is_number('123a')
False
>>> is_number('123.12')
True
>>> is_number('3.0')
True

edited Jul 26 '22 at 20:17

answered Jul 26 '22 at 20:08

PApostol

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How can I tell if a string in python is either an int or float using if condition?

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