finding the index of an item in a pandas df

In [48]: a
Out[48]: 
   c1  c2
0   0   1
1   2   3
2   4   5
3   6   7
4   8   9

In [49]: a.c1[a.c1 == 8].index.tolist()
Out[49]: [4]

Here is what the above code is Doing:
1. a.c1[a.c1 == 8] returns a series with index 4 and value 8.
2. a.c1[a.c1 == 8].index returns the index of the series.
3. a.c1[a.c1 == 8].index.tolist() returns the index of the series as a list.