copy
is defined as a helper to do a copy of the underlying arrays, and the function does not copy the index. See the source code:
Definition: series.copy(self, order='C')
Source:
def copy(self, order='C'):
"""
Return new Series with copy of underlying values
Returns
-------
cp : Series
"""
return Series(self.values.copy(order), index=self.index,
name=self.name)
The index
remains shared by construction. If you want a deeper copy, then just use directly the Series
constructor:
series = pd.Series(range(3))
...: series_copy = pd.Series(series.values.copy(), index=series.index.copy(),
...: name=series.name)
...: series_copy.index += 1
series
Out[72]:
0 0
1 1
2 2
dtype: int64
series_copy
Out[73]:
1 0
2 1
3 2
dtype: int64
In 0.13, copy(deep=True)
is the default interface for copy that will solve your issue. (Fix is here)