Pandas DataFrames are fantastic. However, concatenating them using standard approaches,
such as pandas.concat(), can be very slow with large dataframes.
This is a work around for that problem.
Note: this approach assumes that:
(a) the goal is a row-wise concatenation (i.e., axis=0) and
(b) all dataframes share the same column names.
If these assumptions are not met, this approach could still work…but it will likely need to be modified.