I would like to implement a simple logic:

if Df1 is empty return Df2 else newDf = Df1.union(Df2)

May happened that Df1 is empty and the output is simply: []. In that case I do not need union.

I have it like this but getting error when creating dataframe

if len(Df1) == 0:
  Df2
else:
  newDf=Df1.union(Df2)