CODEWITHSUNDEEP
pythonoopinheritancemodule
dandelion
dandelion

Reputation: 1782

Python - How to change a module implementation?

I want to use python-twitter, but extend the Status class to add a few new methods and attributes. What's the pythonic way to do this?

At the moment, I have functions which add attributes and new functionality to a Status, e.g. 

process_status(status):
    status.datetime = ...
    status.phrase = ...

prettyprint_status(status):
    # do something...

Naturally, I'd just like to add the extra methods to the Status constructor. I found a stackoverflow question discussing this which proposed making a new module, ext-twitter, which contains new implementations of each class, like follows: 

# ext_twitter.py
import twitter

class Api(twitter.Api):
    pass

class Status(twitter.Status):
    def __init__(self, *args):
        twitter.Status.__init__(self, *args)
        self.args = args
        self.time = parseTime(self.created_at)
        self.phrase = ...

    def prettyprint(self):
        # something

However, this doesn't work since the Status classes are generated by the Twitter API object, and here ext-twitter.Api() calls python-twitter.Api() which has no reference to my extended Status class.

Any way to add my functionality to the python-twitter module without forking it and making my own version?

Upvotes: 3

Views: 513

Answers (2)

asermax
asermax

Reputation: 3123

Instead of using inheritance, you can use composition to add functionality to the Status object: 

# ext_twitter.py
import twitter

class Api(twitter.Api):
    def method_that_returns_status(self, *args, **kwargs):
        status = super(Api, self).methot_that_returns_status(*args, **kwargs)

        # wrap the original status with your custom status
        return Status(status)


class Status(object):        
    def __init__(self, status):
        self._internal = status

    def __getattr__(self, attr):
        return getattr(self._internal, attr)

    def __setattr__(self, attr, value):
        if attr == '_internal':
            super(Status, self).__setattr__(attr, value)
        else:
            setattr(self._internal, attr, value)

    def prettyprint(self):
        # something

Upvotes: 1

Marcin
Marcin

Reputation: 49816

Try this:

# patch_twitter.py
import twitter

TwitterStatus = twitter.Status

class Status(TwitterStatus):
     def __init__(self, *args, **kwargs):
        TwitterStatus.__init__(self, *args, **kwargs)
        self.args = args
        self.time = parseTime(self.created_at)
        self.phrase = ...

    def prettyprint(self):
        # something

twitter.Status = Status

# use api

This should work, at least for some values of "work". If there's anything else that captures a reference to the class object originally stored in twitter.Status, then those references won't be updated. That doesn't happen too often, but it could be a source of subtle bugs.

You'll need to import this immediately after importing twitter.py and before doing anything else.

Upvotes: 2

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