Pandas concat yields ValueError: Plan shapes are not aligned

Question

In pandas, I am attempting to concatenate a set of dataframes and I am getting this error:

ValueError: Plan shapes are not aligned

My underst

Answer 1

In case it helps, I have also hit this error when I tried to concatenate two data frames (and as of the time of writing this is the only related hit I can find on google other than the source code).

I don't know whether this answer would have solved the OP's problem (since he/she didn't post enough information), but for me, this was caused when I tried to concat dataframe df1 with columns ['A', 'B', 'B', 'C'] (see the duplicate column headings?) with dataframe df2 with columns ['A', 'B']. Understandably the duplication caused pandas to throw a wobbly. Change df1 to ['A', 'B', 'C'] (i.e. drop one of the duplicate columns) and everything works fine.