Port df.combine_first and/or df.update

[joshuakoh1]

Trying to merge two dfs and overwrite the columns with one df. Using dfd.merge simply renames the duplicate column with _1. Pandas has two functions that provide the required functionality.

https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.combine_first.html https://pandas.pydata.org/pandas-docs/stable/user_guide/merging.html