Preventing users from creating objects of certain classes in Python

Question

I am creating a wrapper Python API for twitter,

For example:

search_tweets(**kwargs)

This API returns back a Tweet object. Tweet class looks something like:

class Tweet:
    def __init__(self, tweet, favorites, impressions, engagements, **kwargs):
        """ Create a new Tweet Object with field values """
        self.impressions = impressions
        self.favorites = favorites
        self.tweet = tweet
        self.engagements = engagements
        vars(self).update(kwargs)


    def retweet():
       """ Retweet this tweet """

Tweet object will be exposed to users because Tweet object will be returned by search_tweets API and users can call methods like retweet on this object, but I do not want users to explicitly create this object.

How can I denote that Tweet object should not be created by users, it should only be operated upon?

def __init__(self, tweet, favorites, impressions, engagements, do_i_know_what_im_doing, **kwargs): if do_i_know_what_im_doing !='yes_i_do': raise RuntimeError — DonQuiKong
– DonQuiKong, Commented Nov 2, 2018 at 9:58

trolley813 · Accepted Answer · 2018-11-02 10:04:51Z

1

You can make Tweet class local to the function, for example:

def search_tweets(**kwargs):
    class Tweet:
        ...

So, the user can call retweet() and other methods on objects returned from search_tweets() function, but cannot easily create Tweet objects by hand due to the lack of human-readable name. But the drawback of this approach is that it will be equally difficult to create Tweets from other API functions.

answered Nov 2, 2018 at 10:04

trolley813

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1 Comment

ThinkGeek Over a year ago

Correct, with this approach it will be difficult to create Tweets from other API functions. I am sure if this is a very generic use-case and people would have thought multiple solutions for this.

Fred · Accepted Answer · 2018-11-02 10:14:30Z

1

You could use the single underscore convention (PEP documentation).

_single_leading_underscore: weak "internal use" indicator. E.g. from M import * does not import objects whose name starts with an underscore.

There is nothing "private" in Python, without having to jump through a bunch of hoops. The best thing you can do is follow convention and comment the class well.

answered Nov 2, 2018 at 10:14

Fred

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1 Comment

ThinkGeek Over a year ago

_single_leading_underscore, I think this will give a wrong impression that the class in private? But users are still using methods on this class for example retweet()

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