Today I learned how to check for multiple types in Python -in a single line-.

TL;DR:

You can pass all types to check in a tuple to the isinstance function (or use typing.Union in Python 3.10+).

I discovered this while reading parts of the implementation of mcp2py. I came across a call to isinstance where the classinfo parameter is a tuple (if isinstance(roots, (str, Path)):), which was new to me.

I checked the Python docs, took a very quick look at the isinstance(object, classinfo, /) documentation, only to find zero examples of its usage (the absence of examples in the Python doc frustrates me everytime,and I prefer reading examples first), then I asked ChatGPT, who explained that the line checks if roots is a str or a pathlib.Path object. I came back to double check in Python docs, which confirmed ChatGPT claims:

If classinfo is a tuple of type objects (or recursively, other such tuples) or a Union Type of multiple types, return True if object is an instance of any of the types

So I learned that instead of calling isinstance multiple times for each type, I can simply do:

from typing import Union
from pathlib import Path

str_path = "path/to/file.txt"
path_obj = Path("path/to/file.txt")

isinstance(str_path, (Path, str))  # True
isinstance(path_obj, (Path, str))  # True, too