multiple row selection in multi indexed dataframe

Question

Suppose I write this code in pandas to create a dataframe:

pd.DataFrame({'x':random.sample(range(1,100), 4),
         'y':random.sample(range(1,100), 4),
         'z':random.sample(range(1,100), 4)},
          index = [['a1', 'b1', 'c1','d1'], ['a2', 'b2', 'c2', 'd2']])

This results in the following dataframe:

            x   y   z
    a1  a2  8   2   85
    b1  b2  43  93  58
    c1  c2  1   46  24
    d1  d2  60  37  62

I want to select the multi indexed rows by passing a list like:

[[a1, a2], [b1, b2], [c1, c2]]

to return:

            x   y   z
    a1  a2  8   2   85
    b1  b2  43  93  58
    c1  c2  1   46  24

Is there a function in pandas that does it?

Answer 1

You were very close: you need to define the indexes as a list of tuples and not as a list of lists:

target_index = [('a1', 'a2'), ('b1', 'b2'), ('c1', 'c2')]

Then

df.loc[target_index]

gives you the desired output:

       x  y  z
a1 a2  0  2  3
b1 b2  1  3  4
c1 c2  2  4  5