Python isnumeric negative numbers

You can not check negative numbers with the isnumeric function in Python. Python isnumeric()is used to check whether a given string consists of only numeric characters or not. However, this method does not consider negative numbers as numeric characters.

Python isnumeric negative numbers example

Simple example code isnumeric() method returns True for the string "123", but it returns False for the string "-123".

a = "123"
print(a, a.isnumeric())

b = "-123"
print(b, b.isnumeric())

Output:

Alternatively, you can use a regular expression to check whether a given string represents a negative number or not.

import re


def is_number(s):
    return bool(re.match(r'^-?\d+(?:\.\d+)?$', s))


print(is_number('123')) # True
print(is_number('-123')) # True
print(is_number('A1')) #False

One simple way to check if a string is a number or not is to try to convert it to a number using a built-in Python function like int() or float(). If the conversion succeeds, then the string is a number; otherwise, an exception will be raised.

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

Note: the isdigit() method does not consider negative numbers as numeric characters.

Do comment if you have any doubts or suggestions on this Python isnumeric function topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.