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Date: Mon, 13 Feb 2012 18:53:27 +0100
From: Fabrizio Pollastri <f.pollastri@inrim.it>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:20353

Ok. To be more clear, consider the real python package Pandas.

This package defines a Series class and a DataFrame class.
The DataFrame is a matrix that can have columns of
different type.

If I write

import pandas as pd
df = pd.DataFrame({'A':[1,2,3],'B':[4,5,6]})

a data frame with two cols named A and B is created.

If I write

col_A = df['A']

the returned col_A is an instance of Series.

Now , let suppose that I want to extend some functionality of pandas
by adding new methods to both Series and DataFrame classes.

One way to do this is to redefine this classes in a new package
(new_pandas) as follow

import pandas as pd

class Series(pd.Series):
      ...
      add new methods
      ...

class DataFrame(pd.DataFrame):
      ...
      add new methods
      ...

When I use the new package as a pandas substitute and write

import new_pandas as np
df = np.DataFrame({'A':[1,2,3],'B':[4,5,6]})
col_A = df['A']

col_A is an instance of the original pandas and not of the new pandas, 
losing all the added functionality.


Fabrizio











Now, how can I add new methods to extend the functionality of pandas 
classes Series and DataFrame