In scientific code that deals with mathematical operations, before type annotations, it is common to assume that any mathematical function could take in a numpy array. To be explicit you just add to your docstring that you can take array_like
or ndarray
(as is conventional in NumFocus project docs).
Today, with type annotations, I am at a lost on how to annotate something as simple as:
import numpy as np
def get_variance_plus_one(sample): # A stupid function, just for example
return 1 + np.var(sample)
What is the proper type for sample
?

Any  Sequence[Any]
: Too generic for numerical math. Does not support numpy arrays 
float  Sequence[float]
: Does not support complex number (rare usecase) or numpy arrays. 
number.Number  Sequence[number.Number]
: Does not support numpy arrays. 
np.typing.ArrayLike
: Too generic so much so that__add__
and__mul__
aren’t necessary. Look at this Pylance error:Operator "+" not supported for types "ArrayLike" and "ArrayLike" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "_SupportsArray[dtype[Unknown]]" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "_NestedSequence[_SupportsArray[dtype[Unknown]]]" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "bool" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "int" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "float" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "complex" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "str" Operator "+" not supported for types "_SupportsArray[dtype[Unknown]]" and "bytes

np.typing.NDArray[np.number]
: Similar problem toArrayLike

np.typing.NDArray[np.integer  np.floating  np.complexfloating  ...? ]  number.Number
This is way too verbose and prone to mistakes!
Apologies if this issue is better addressed to NumPy. Feel free to send me a link to the relevant community channel.