I'm having a problem I haven't seen elsewhere (and apologies if it has been answered before).

I see the following behavior (copied verbatim from a python session):

Python 2.7.4 (default, Apr  6 2013, 19:55:15) [MSC v.1500 64 bit (AMD64)] on win32
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>>> import numpy as np
>>> x=[[np.zeros(10)] for i in range(10)]
>>> x.index(x[0])
0
>>> x.index(x[1])
Traceback (most recent call last):
  File "", line 1, in 
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
>>> x[1].append(np.zeros(10))
>>> x.index(x[1])
1

Any ideas why I see a ValueError when trying to find the index of a list containing a single ndarray?