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Finding the index of an item in embedded sequences (Python recipe) by Brett Cannon
ActiveState Code (http://code.activestate.com/recipes/65252/)

This function will return a list containing the indices needed to reach an item in embedded sequences.

So deepindex([[1,2],[3,[4,[5,6]]],7,[8,9]],6) will return [1,1,1,1].

Python, 20 lines
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from __future__ import nested_scopes
import types

found='found'

def deepindex(sequence, goal):
    """deepindex(sequence,goal) -> index list"""
    def helper(sequence,index_list):
        for item in sequence:
            if item==goal:
                index_list.append(sequence.index(item))
                raise found,index_list
            elif isinstance(item,types.ListType) or isinstance(item,types.TupleType):
                index_list.append(sequence.index(item))
                index_list=helper(item,index_list)
        else: return index_list[:-1]

    try: helper(sequence,[])
    except found,index_list: return index_list
    else: return -1

This is handy for when you have very deep sequences and you need something better than list.index(item). It also, obviously, functions as a way to find out if something is in a deep sequence, regardless of whether you need to know its location within the sequence.

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