df.Change[-1] producing errors. - pandas

Question

I'm trying to slice the last value of the series Change from my dataframe df.
The dataframe looks something like this
Change
0 1.000000
1 0.917727
2 1.000000
3 0.914773
4 0.933182
5 0.936136
6 0.957500
14466949 1.998392
14466950 2.002413
14466951 1.998392
14466952 1.974266
14466953 1.966224
When I input the following code
df.Change[0]
df.Change[100]
df.Change[100000]
I'm getting an output, but when I'm input
df.Change[-1]
I'm getting the following error
Traceback (most recent call last):
File "<pyshell#188>", line 1, in <module>
df.Change[-1]
File "C:\Python27\lib\site-packages\pandas\core\series.py", line 601, in __getitem__
result = self.index.get_value(self, key)
File "C:\Python27\lib\site-packages\pandas\indexes\base.py", line 2139, in get_value
tz=getattr(series.dtype, 'tz', None))
File "pandas/index.pyx", line 105, in pandas.index.IndexEngine.get_value (pandas\index.c:3338)
File "pandas/index.pyx", line 113, in pandas.index.IndexEngine.get_value (pandas\index.c:3041)
File "pandas/index.pyx", line 151, in pandas.index.IndexEngine.get_loc (pandas\index.c:3898)
KeyError: -1
Pretty much any negative number I use for slicing is resulting in an error, and I'm not exactly sure why.
Thanks.

Answer 1

There are several ways to do this. What's happening is that pandas has no issues with df.Change[100] because 100 is in its index. -1 is not. You happen to have your index the same as if you were using ordinal positions. To explicitly get ordinal positions, use iloc.
df.Change.iloc[-1]
or
df.Change.values[-1]