I have a dataframe with the following information:

I want to add a column called Final Date, which is the maximum value of the three columns, and where a column is null I want it to be ignored.

I have tried the following code to add a column:

df['Initial_Date']=pd.to_datetime(df['Initial_Date'],errors='coerce')
df['First_Revision_Date']=pd.to_datetime(df['First_Revision_Date'],errors='coerce')
df['Second_Revision_Date']=pd.to_datetime(df['Second_Revision_Date'],errors='coerce')

df.insert(len(df.columns),'Final_Date',allow_duplicates = False, value=df['Initial_Date','First_Revision_Date','Second_Revision_Date'].max(axis=1))

Error:

   3801     #  InvalidIndexError. Otherwise we fall through and re-raise
   3802     #  the TypeError.
   3803     self._check_indexing_error(key)