Treat Series as 1-column dataframe in concat with dataframe · Issue #15047 · pandas-dev/pandas (original) (raw)

When concatenating a dataframe and series along axis 1, the docs indicate that the series will be treated as a series with a single column matching the column name. Based on this, I'd expect similar behavior (or an error) when concatenating a named series with a dataframe along axis 0. However, this seems to result in a new numeric column for the named series instead of converting the series to a dataframe:

In [10]: pd.version Out[10]: '0.19.1'

In [11]: df = pd.DataFrame({'x': range(5), 'y': range(5), 'z': range(5)})

In [12]: pd.concat([df, df.x]) Out[12]: x y z 0 0 0.0 0.0 0.0 NaN 1 1.0 1.0 1.0 NaN 2 2.0 2.0 2.0 NaN 3 3.0 3.0 3.0 NaN 4 4.0 4.0 4.0 NaN 0 NaN NaN NaN 0.0 1 NaN NaN NaN 1.0 2 NaN NaN NaN 2.0 3 NaN NaN NaN 3.0 4 NaN NaN NaN 4.0

In [13]: pd.concat([df, df.x.to_frame()]) Out[13]: x y z 0 0 0.0 0.0 1 1 1.0 1.0 2 2 2.0 2.0 3 3 3.0 3.0 4 4 4.0 4.0 0 0 NaN NaN 1 1 NaN NaN 2 2 NaN NaN 3 3 NaN NaN 4 4 NaN NaN

I'd expect either an error, or the behavior in out[13].