How to change the list[str] annotation so that it accepts list[LiteralString] too?
![How to change the list[str] annotation so that it accepts list[LiteralString] too?](/_next/image?url=https%3A%2F%2Fcdn.sanity.io%2Fimages%2F80wy3gkl%2Fproduction%2F497db7c448a30b6bf2565bea31f7ffdee4651405-1280x720.png&w=3840&q=75)
python
Ethan JacksonI have a function that takes a list of str as an input
def function(names: list[str]) -> None:
for name in names:
print(name)
If I generate the list using the split() function, I end up with an object of type list[LiteralString] so mypy marks it an error
names = "Jürgen Klopp".split()
function(names) # Argument of type "list[LiteralString]" cannot be assigned to parameter "names" of type "list[str]" in function "function"
I would like to know how the LiteralString is expected to be used with lists?
I can build myself a type like
StrListType = list[str] | list[LiteralString]
but this workaround is not needed when using non-listed objects, i.e.,
def fn(name: str):
print(name)
names = "Jürgen Klopp".split()
given_name: LiteralString = names[0]
fn(given_name) # No problems
Answer
You can use a covariant type like Sequence[str], it is a clean solution because it lets your function accept any sequence of strings including the list returned by .split()
from collections.abc import Sequence
def print_names(names: Sequence[str]) -> None:
for name in names:
print(name)
names = "Jürgen Klopp".split()
print_names(names)
Output
Jürgen
Klopp