Why pandas act different when I use just python?
## I write a short program like this:
# coding: utf-8

from pandas import DataFrame
from string import letters

df = DataFrame(
    {'a': range(0, 10), 'b': range(10, 20), 'c': range(20, 30)},
    index=list(letters[:10])
)
rec = df.ix['A']
rec['a'] = 1 
print df
## When I run it with ipython, everything is fine!
## $ ipython test.py

   a   b   c
A  1  10  20
B  1  11  21
C  2  12  22
D  3  13  23
E  4  14  24
F  5  15  25
G  6  16  26
H  7  17  27
I  8  18  28
J  9  19  29
## But when I run it just use python,I get this below:
## $ python test.py

Traceback (most recent call last):
  File "test.py", line 9, in <module>
    rec = df.ix['A']
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.16.2-py2.7-linux-x86_64.egg/pandas/core/indexing.py", line 70, in **getitem**
    return self._getitem_axis(key, axis=0)
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.16.2-py2.7-linux-x86_64.egg/pandas/core/indexing.py", line 929, in _getitem_axis
    return self._get_label(key, axis=axis)
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.16.2-py2.7-linux-x86_64.egg/pandas/core/indexing.py", line 86, in _get_label
    return self.obj._xs(label, axis=axis)
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.16.2-py2.7-linux-x86_64.egg/pandas/core/generic.py", line 1473, in xs
    loc = self.index.get_loc(key)
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.16.2-py2.7-linux-x86_64.egg/pandas/core/index.py", line 1572, in get_loc
    return self._engine.get_loc(_values_from_object(key))
  File "pandas/index.pyx", line 134, in pandas.index.IndexEngine.get_loc (pandas/index.c:3824)
  File "pandas/index.pyx", line 154, in pandas.index.IndexEngine.get_loc (pandas/index.c:3704)
  File "pandas/hashtable.pyx", line 686, in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12280)
  File "pandas/hashtable.pyx", line 694, in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12231)
KeyError: 'A'
## Why pandas act different when I use just python?

python version = 2.7.6
ipython version = 4.0.0
pandas version = 0.16.2
