[Doc]: Linting the example from the README gives an error when using ty. #3493
Description
What type of report is this?
Correction
Please describe the issue.
Recall the example from the README:
import narwhals as nw
from narwhals.typing import IntoFrameT
def agnostic_function(
df_native: IntoFrameT,
date_column: str,
price_column: str,
) -> IntoFrameT:
return (
nw.from_native(df_native)
.group_by(nw.col(date_column).dt.truncate("1mo"))
.agg(nw.col(price_column).mean())
.sort(date_column)
.to_native()
)When I check this with ty via uvx -w narwhals ty check tmp1.py, I get:
uvx -w narwhals ty check tmp1.py
error[unresolved-attribute]: Attribute `group_by` is not defined on `Series[Unknown]` in union `DataFrame[Unknown] | Series[Unknown]`
--> tmp1.py:11:9
|
9 | ) -> IntoFrameT:
10 | return (
11 | / nw.from_native(df_native)
12 | | .group_by(nw.col(date_column).dt.truncate("1mo"))
| |_________________^
13 | .agg(nw.col(price_column).mean())
14 | .sort(date_column)
|
info: rule `unresolved-attribute` is enabled by default
Found 1 diagnostic
Whereas if I rewrite this by replacing IntoFrameT with IntoDataFrameT, all checks pass.
import narwhals as nw
from narwhals.typing import IntoDataFrameT
def agnostic_function(
df_native: IntoDataFrameT,
date_column: str,
price_column: str,
) -> IntoDataFrameT:
return (
nw.from_native(df_native)
.group_by(nw.col(date_column).dt.truncate("1mo"))
.agg(nw.col(price_column).mean())
.sort(date_column)
.to_native()
)No issues here:
uvx -w narwhals ty check tmp2.py
All checks passed!
If you have a suggestion on how it should be, add it below.
I'd expect the example in the README to pass a check from ty. I am not sure if this is as simple as just swapping IntoFrameT with IntoDataFrameT in the README, of if this is deeper, underlying problem.