Python: How to extend a class?

Question

So, I really want to add on a few new methods to pandas.core.frame.DataFrame s. For example, I want a method called .idx :

pandas.core.frame.DataFrame.idx(self, rows, cols):
    return self.iloc[rows].loc[cols]

Is this possible? I'm not sure what the syntax should be - the class already exists from a library, so I can't just put the function inside the class definition.

Answer 1

Could you not extend your DataFrame , inheriting all of its functions, and having the freedom to then define your own, on top?

In python it would look something like:

class ExtendedDataFrame(DataFrame):
    ...

Then, simply use an instance of ExtendedDataFrame , instead of DataFrame , for your extra goodies.

I also suggest taking a look at this tutorial covering inheritance.

Also be sure to check out your version of python's implementation of super() , if you're trying to override functions of the super (parent) class.

Here is a SO question with great information regarding super() , because I'm noticing the tutorial I linked only briefly covers super() , and in the comments no less.

Answer 2

This is actually really easy in Python. While I would recommend inheriting from DataFrame, as MeetTitan answered, sometimes that won't work, but you can just add on functions like this:

class Abc(object):
    pass

def new_funct(self):
    print 1234

Abc.instance_funct = new_funct
a = Abc()
a.instance_funct()