Given the following two DataFrames :
df1
  unicorn  size
0    blue     3
1     red     4
2    piNk     6
df2
  unicorn  size
0    blue     1
1     red     2
How can I apply the rows of both dataframes column-wise using custom functions like this (simplified):
def some_operation(a, b):
  return # some operations
Expected result:
   size A size B. result
0    3.     1.      3
1.   3.     2.      6
2    4.     1.      4
3.   4.     2.      8
4    6.     1.      6
5.   6.     2.      12
