pandas: Boolean indexing with multi index

Question

There are many questions here with similar titles, but I couldn\'t find one that\'s addressing this issue.

I have dataframes from many different origins, and I want to f

Answer 1

If the boolean series is not aligned with the dataframe you want to index it with, you can first explicitely align it with align:

In [25]: df_aligned, filt_aligned = df.align(filt.to_frame(), level=0, axis=0)

In [26]: filt_aligned
Out[26]:
         0
a b
1 1   True
  2   True
  3   True
2 1  False
  2  False
  3  False
3 1   True
  2   True
  3   True

And then you can index with it:

In [27]: df[filt_aligned[0]]
Out[27]:
     c
a b
1 1  0
  2  1
  3  2
3 1  6
  2  7
  3  8

Note: the align didn't work with a Series, therefore the to_frame in the align call, and therefore the [0] above to get back the series.