A new string method, .isnumber()

[rxzzakcodes]

Feature or enhancement

Proposal:

A string method called .isnumber(), it will check if a string is a float or an integer and return True or False.

def isnumber(text)
    try:
        float(text)
        return True
    except ValueError:
        return False

Examples:

abc = "123"
pi = "3.14159"
hello = "hello"

print(isnumber(abc)) # True
print(isnumber(pi)) # True
print(isnumber(hello)) # False

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[rxzzakcodes]

if it was a built in string method, instead of using isnumber(variable), you would do variable.isnumber()

[JelleZijlstra]

str.isnumeric() already exists.

[terryjreedy]

s.isnumeric only works for ints (all digits). For floats, there is usually no need to wrap float()

if fs.isnumber(): <do x>
else: <do y>

is a slower version of

try:
    float(fs)
    <do x>
except ValueError:
    <do y>

In nearly all cases where we want to know if a string can be converted, we want the converted float, and throwing it away just to call float again is poor practice. In Python, try-except is as legitimate as if-else.

Note: New builtin functions are not 'minor features' and always need major discussion and a high bar for adoption. We are also pretty stringent about new methods for built-in classes.