How to filter strings in pandas series index

Question

I'm trying to filter a pandas series by using a boolean expression on its index, which contains strings. For example, in the code below I wish to create a new Series (Sman) by filtering another series (S) for rows where the index items contain the substring 'man':

from pandas import Series
S = Series({'moondog':12,'catman':23, 'batman':31, 'catdog':42})
Sman = S['man' in S]

However, the result for Sman is simply the number 31, and not a new series containing the rows for 'catman' and 'batman' as I was hoping for.

What am I doing wrong??

Answer 1

You can use the filter method:

In [11]: S.filter(like='man')
Out[11]:
batman    31
catman    23
dtype: int64

A manual alternative would be:

In [12]: S[['man' in i for i in S.index]]
Out[12]:
batman    31
catman    23
dtype: int64

The reason your approach did not work is that 'man' in S just returns False, as this checks if the exact label 'man' is contained in the index (which is not the case).