pandas fillna not returning correct type

[Dr-Irv]

Environment data

• Language Server version: 2020.9.8
• OS and version: Windows 10
• Python version (& distribution if applicable, e.g. Anaconda): Anaconda Python 3.7.5

Expected behaviour

No error

Actual behaviour

import pandas as pd
import numpy as np

df: pd.DataFrame = pd.DataFrame({"x": [1, np.nan, 3]})

ndf: pd.DataFrame = df.fillna(-1)

print(ndf)

reports

Expression of type "DataFrame | None" cannot be assigned to declared type "DataFrame"
  Type "DataFrame | None" cannot be assigned to type "DataFrame"
    Type "None" cannot be assigned to type "DataFrame"

Possible fix:

diff frame.pyi.ORIG frame.pyi
756c756
<         inplace: Literal[False]
---
>         inplace: Literal[False] = ...

[jakebailey]

This issue has been fixed in version 2020.10.0, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#2020100-7-october-2020

[Dr-Irv]

@jakebailey I am running the 20.10.0 version now, and this is not fixed.

Here is what I did to that version to fix it:

diff frame.pyi.ORIG frame.pyi
653c653
<         inplace: Literal[True] = ...
---
>         inplace: Literal[True]
760c760
<         inplace: Literal[False]
---
>         inplace: Literal[False] = ...

[jakebailey]

Thanks, I'll fix that.

[jakebailey]

This issue has been fixed in version 2020.10.1, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#2020101-14-october-2020