How to type hint an (arbitrary) collection of some data type in Python?-CodePudding

If I have a function similar to:

def some_function(paths):
    for path in paths:
        other_function(path)

what is the correct way to type hint paths? The intention of the function is that each object inside paths is a string, but obviously paths could be a list, tuple, set, numpy array, pandas Series etc. so the following seems too specific:

def some_function(paths: list[str]):
    for path in paths:
        other_function(path)

Should I be using either Collection or Sequence from the typing module?

CodePudding user response：

Since the only thing you rely on here is iterability, ask for that.

from typing import Iterable

def some_function(paths: Iterable[str]):
    for path in paths:
        other_function(path)

If these really are supposed to be file-system paths, you might tweak it to allow str or anything supporting the os.PathLike ABC:

import os
from typing import Iterable

def some_function(paths: Iterable[str | os.PathLike]):  # On older Python, Iterable[Union[str, os.PathLike]]
    for path in paths:
        other_function(path)

CodePudding user response：

If you want paths to be just a string then,

def some_function(paths: str):

If you want the function to accept any number of strings you can use the * operator

def some_function(*paths: str):

Keep in mind type hinting is only a suggestion, python will not test for correct input argument type.