BUG: ValueError when indexing using range only when length >= 1,000,000

[nekobon]

From SO (http://stackoverflow.com/questions/33814223/strange-error-in-pandas-indexing-with-range-when-length-1-000-000)

Pandas raises a ValueError when assigning multiple values to a Series (or DataFrame) using range(x) where x > 1. This error is raised only when its length is one million or larger.

import pandas as pd

for x in [5, 999999, 1000000]:
    s = pd.Series(index=range(x))
    print('series length =', len(s))
    # assigning value with range(1), always works
    s.loc[range(1)] = 42 
    # reading values with range(x>1), always works
    _ = s.loc[range(2)] 
    # assigning values with range(x>1), fails only when len >= 1 million
    s.loc[range(2)] = 42 

Output:

series length = 5
series length = 999999
series length = 1000000
Traceback (most recent call last):
  File "<stdin>", line 9, in <module>
  File "/home/nekobon/.env_exp/lib/python3.4/site-packages/pandas/core/indexing.py", line 114, in __setitem__
    indexer = self._get_setitem_indexer(key)
  File "/home/nekobon/.env_exp/lib/python3.4/site-packages/pandas/core/indexing.py", line 109, in _get_setitem_indexer
    return self._convert_to_indexer(key, is_setter=True)
  File "/home/nekobon/.env_exp/lib/python3.4/site-packages/pandas/core/indexing.py", line 1042, in _convert_to_indexer
    return labels.get_loc(obj)
  File "/home/nekobon/.env_exp/lib/python3.4/site-packages/pandas/core/index.py", line 1692, in get_loc
    return self._engine.get_loc(_values_from_object(key))
  File "pandas/index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas/index.c:3979)
  File "pandas/index.pyx", line 145, in pandas.index.IndexEngine.get_loc (pandas/index.c:3680)
  File "pandas/index.pyx", line 464, in pandas.index._bin_search (pandas/index.c:9124)
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Tested on pandas 0.17.0 and python 3.4.

[jreback]

odd, only happens on py3.

[nekobon]

range(2) is a list in py2.x. s.loc[list[range(2)]] = 42 works fine with py3, too.
It seems to be failing only with range object.

[jreback]

note that this was never supported, but fixed in #11653