How do I select rows from a DataFrame based on column values with given conditions?

Question

How to apply rules in python, if i want A, B = 1,2 and C,D = 3,4 and E,F = 5,6 each and drop the remaining

    Type       Set
1    A          1
2    B          2           
3    B          3
4    C          4
5    D          5
6    A          2
7    F          3
8    F          2
9    E          1
10   D          5
11   E          5
12   C          6

i tried using drop but its lengthy

Answer 1

What about using multiple masks:

m1 = df['Type'].isin(['A', 'B'])
m2 = df['Type'].isin(['C', 'D'])

m3 = df['Set'].isin([1, 2])
m4 = df['Set'].isin([3, 4])

out = df.loc[(m1&m3)|(m2&m4)]

Or:

m1 = df['Type'].isin(['A', 'B'])
m2 = df['Type'].isin(['C', 'D'])

m3 = df.loc[m1, 'Set'].isin([1, 2]).reindex(df.index, fill_value=False)
m4 = df.loc[m2, 'Set'].isin([3, 4])

out = df.loc[m3 | m4]

Output:

  Type  Set
1    A    1
2    B    2
4    C    4
6    A    2
7    C    3
9    B    1