pandas (original) (raw)

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 "", line 9, in 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.