how to expand each unique value in another column and fill zero if no match

[SriRajesh]

Hi,
I have below df:

first_name second_name  X     Y      count
A              A1                  0.1   0.4    1
A              A1                  0.2   0.2    2
B              B1                  0.1   0.1    2
B              B1                  0.2   0.2    5


[python]desired output:

first_name  second_name  X     Y      count
A              A1                  0.1   0.4    1
A              A1                  0.2   0.2    2
A              A1                  0.1   0.1    0
B              B1                  0.1   0.1    2
B              B1                  0.2   0.2    5
B              B1                  0.1   0.4    0

X Y
0.1 0.4 this combination exists in A & A1 but not in B& B1. This combination will extend to B & B1 and count is "0"