Here’s a fun thing with Python’s type annotations.
Sometimes one might use Iterable as a type annotation to try to indicate something might be a set, a list, or a
tuple.
But Iterable really just means something that implements
__iter__().
And str implements __iter__(), e.g.:
for char in "abc":
print(char)
# a
# b
# c
And “a” is a str, just like “abc” is a str.
So this type checks: my_var: Iterable[str] = "abc" (!!!).
from typing import Iterable, List
# these all pass type check
a: str = "a"
b: Iterable[str] = "abc" # woops?
c: Iterable[str] = ["abc", "def"]
# this fails type check
d: List[str] = "abc"
A fun footgun to be aware of :). Get more specific with types to avoid unexpectedly correct-but-not-what-was-meant annotations.