Pycharm linter flags output of concat as "type", not DataFrame

Minimum display example

df1 = pd.DataFrame({'A': ['A0']}, index=[0])
df2 = pd.DataFrame({'A': ['A4']}, index=[4])
result = pd.concat([df1, df2])

print(df1.loc[4])  # Pycharm doesn't flag
print(result.loc[4])  # Pycharm flags as "Unresolved attribute reference '.loc' for class 'type'"
                      # But runs fine anyway

Problem description

Pycharm’s linter believes pd.concat as returning class “type”, when it normally returns a dataframe.

I suspect that this is due to core.reshape.concat._Concatenator.get_result() using core.dtypes.concat._get_frame_result_type which sometimes returns SparseDataFrame (a type) and sometimes an object (normally a Dataframe?).

Extract from pandas.core.dtypes.concat

def _get_frame_result_type(result, objs):
    """
    return appropriate class of DataFrame-like concat
    if any block is SparseBlock, return SparseDataFrame
    otherwise, return 1st obj
    """
    if any(b.is_sparse for b in result.blocks):
        from pandas.core.sparse.api import SparseDataFrame
        return SparseDataFrame
    else:
        return objs[0]

Expected Output

The MDE should not throw an error in Pycharm.

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.6.2.final.0 python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel byteorder: little LC_ALL: None LANG: None LOCALE: None.None

pandas: 0.20.3 pytest: None pip: 9.0.1 setuptools: 28.8.0 Cython: None numpy: 1.13.1 scipy: None xarray: None IPython: None sphinx: None patsy: None dateutil: 2.6.1 pytz: 2017.2 blosc: None bottleneck: None tables: None numexpr: None feather: None matplotlib: None openpyxl: 2.4.8 xlrd: None xlwt: None xlsxwriter: None lxml: None bs4: 4.6.0 html5lib: None sqlalchemy: None pymysql: None psycopg2: None jinja2: None s3fs: None pandas_gbq: None pandas_datareader: None None

I am using Pycharm Community Edition 2017.1.5.

[jebob]

@gfyoung I’ve been suppressing the warnings in my code using type hints instead. foo = pd.concat([bar1, bar2]) # type: pd.DataFrame

[gfyoung]

• The issue is unrelated to your PyCharm version
• It should be addressed in 0.23.0