mypy, type hint: Union[float, int] -> is there a Number type?
Use float
only, as int
is implied in that type:
def my_func(number: float):
PEP 484 Type Hints specifically states that:
Rather than requiring that users write import numbers and then use
numbers.Float
etc., this PEP proposes a straightforward shortcut that is almost as effective: when an argument is annotated as having typefloat
, an argument of typeint
is acceptable; similar, for an argument annotated as having type complex, arguments of type float or int are acceptable.
(Bold emphasis mine).
Ideally you would still use numbers.Real
:
from numbers import Realdef my_func(number: Real):
as that would accept fractions.Fraction()
and decimal.Decimal()
objects as well; the number pyramid is broader than just integers and floating point values.
However, these are not currently working when using mypy
to do your type checking, see Mypy #3186.
For people who come to this question for the more general problem of Union typing hints for entities which don't have an existing supertype in common, for example Union[int, numpy.ndarray]
, the solution is to import Union
from typing
.
Example 1:
from typing import Uniondef my_func(number: Union[float, int]): # Do something
Example 2:
from typing import Unionimport numpy as npdef my_func(x: Union[float, np.ndarray]): # do something # Do something
You can define your own type to address this and keep your code cleaner.
FloatInt = Union[float, int]def my_func(number: FloatInt): # Do something