Typing Number, PyCharm

[Weatherby,Gerard]

dn,

I’m missing something here. Method 5 seems to work fine in PyCharm. I’m interpreting your statement as:

from fractions import Fraction
from numbers import Number


def double(value: Number):
    if isinstance(value, Number):
        # noinspection PyTypeChecker
        return 2 * value
    raise ValueError(f"{value} of {type(value)} is not a Number")


print(double(7))
print(double(7.2))
print(double(complex(3.2, 4.5)))
print(double(Fraction(7, 8)))
# print(double("7")) PyCharm properly complains


From: Python-list <python-list-bounces+gweatherby=uchc.edu at python.org> on behalf of dn via Python-list <python-list at python.org>
Date: Saturday, February 4, 2023 at 9:32 PM
To: 'Python' <python-list at python.org>
Subject: Typing Number, PyCharm
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Do we have a typing type-hint for numbers yet?


Often wanting to combine int and float, discovered that an application
was doing a walk-through with/for uses three numeric types. Was
intrigued to note variance, in that the code-set features two different
methods for typing, in this situation:

def func( value ):
     ...using value...

where value may be an integer, a floating-point value, or a
complex-number (but not decimal-type).
NB code snippets from memory (cf copy-paste)


Method 1 (possibly older code):-

from typing import Union
...
def fun( value:Union[ int, float, complex ] ):


Method 2:-

def fun( value:int|float|complex  ):


Pondering this, realised could use an alias to de-clutter the
function-definition/signature:

Method 3:-

number_type = int|float|complex
...
def fun( value:number_type  ):


If it was important to have type consistency within the union, eg
argument and return, could go for:

Method 4:-

from typing import TypeVar
number_type = TypeVar( 'number_type', int, float, complex )
...
def fun( value:number_type  ):


Then remembered the way we'd code an execution-time check for this using
isinstance():

Method 5:-

from numbers import Number
...
def fun( value:Number  ):


Each of these will execute correctly.

All cause PyCharm to object if I try to call the fun(ction) with a
string parameter - and execute an exception, as expected.


Accepting all the others, am curious as to why PyCharm objects to Method
5 with "Expected type 'SupportsFloat | SupportsComplex | complex |
SupportsIndex', got 'Number' instead? - yet still highlights the
erroneous string parameter but none of the 'legal' data-types?

As soon as a list (in this case types) reaches three, my aged-eyes start
to think de-cluttering is a good idea!

Do you know of another way to attack this/more properly?

--
Regards,
=dn
--
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