Caridorc Caridorc - 2 months ago 9
Python Question

`Iterable[(int, int)]` tuple is not allowed in type hints

I have this very simple code:

from typing import List, Iterable

Position = (int, int)
IntegerMatrix = List[List[int]]

def locate_zeros(matrix: IntegerMatrix) -> Iterable[Position]:
"""Given an NxM matrix find the positions that contain a zero."""
for row_num, row in enumerate(matrix):
for col_num, element in enumerate(row):
if element == 0:
yield (col_num, row_num)


This is the error:

Traceback (most recent call last):
File "type_m.py", line 6, in <module>
def locate_zeros(matrix: IntegerMatrix) -> Iterable[Position]:
File "/usr/lib/python3.5/typing.py", line 970, in __getitem__
(len(self.__parameters__), len(params)))
TypeError: Cannot change parameter count from 1 to 2


Why can't I have an iterable of Int pairs as the return type?

Both
-> Position
and
Iterable[Any]
work, just not
Iterable
and
Position
together don't.

Answer

You should use typing.Tuple[int, int] to declare the tuple type Position, not (int, int).

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