False positive for operator in in pandas

[ncarve]

Environment data

• Language Server version: 2020.7.4
• OS and version: Ubuntu 18.04
• Python version (& distribution if applicable, e.g. Anaconda): Python 3.7.7 (Anaconda)
• Pandas version: 1.0.5

Expected behaviour

Pylance should not detect any error when using the in operator on pandas Index objects (for example 'c1' in df.columns)

Actual behaviour

Pylance raises the following error when the in operator is used on a pandas Index object:

Operator "in" not supported for types "str" and "Index[_str]"

The code itself executes just fine. This happens for example when in or not in is used on a DataFrame's columns or index properties.

Code Snippet / Additional information

import pandas as pd

df = pd.DataFrame(columns=['c1', 'c2'], data=[[1, 2], [3, 4]], index=['i1', 'i2'])

if 'c1' in df.columns:
    print('ok')
if 'i1' in df.index:
    print('ok')

[erictraut]

@gramster, this is a bug in the type stub. It's missing the __contains__ magic method in the Index class.

[jakebailey]

This issue has been fixed in version 2020.8.1, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#202081-13-august-2020