[SOLVED] Describing complex return type of the method

Describing complex return type of the method

I'm trying to define return type of the method in Python (3.8.9). Ideally, return type should be list of tuple of int. My first natural solution, as I came from strongly typed world, was def .... -> list(tuple(int,int)).

Unfortunately this doesn't work and bring runtime exception

tuple expected at most 1 argument, got 2

As per documentation section Type Alias defining type like list[int] or tuple[int] should work but in my code I'm getting same error even if C/P code from documentation.

Is type hint feature is version specific? What am I missing?

Solution

You are using round brackets, while the documentation specifies square brackets.

Try this, for example:

def fn() -> list[tuple[int, int]]:
    return [(1, 2), (3, 4)]

Or, if you are using Python versions older than 3.9, try this:

from typing import List, Tuple


def fn() -> List[Tuple[int, int]]:
    return [(1, 2), (3, 4)]