subtracting two dataframes

Question

df1:

City, 2015-12-31, 2016-01-31, ...
YYZ  562.14, -701.18, ...
DFW  562.14, -701.18, ...
YYC  562.14, -701.18, ...

df2:

Answer 1

Does this work?

df2.drop(['City']).subtract(df1.drop(['City']))

Answer 2

Move the City column into the index. The DataFrames will align by both index and columns first and then do subtraction. Any combination not present will result in NaN.

df2.set_index('City').subtract(df1.set_index('City'), fill_value=0)