Getting the integer index of a Pandas DataFrame row fulfilling a condition?

Question

I have the following DataFrame:

   a  b  c
b
2  1  2  3
5  4  5  6

As you can see, column b is used as an index. I want to get

Answer 1

With Index.get_loc and general condition:

>>> import pandas as pd
>>> import numpy as np


>>> df = pd.DataFrame(np.arange(1,7).reshape(2,3),
                  columns = list('abc'),
                  index=pd.Series([2,5], name='b'))
>>> df
   a  b  c
b
2  1  2  3
5  4  5  6
>>> df.index.get_loc(df.index[df['b'] == 5][0])
1