Comment by ok123456
7 days ago
If you're inheriting from dict to extend its behavior, there are a lot of side effects with that, and it's recommended to use https://docs.python.org/3/library/collections.html#collectio... instead.
7 days ago
If you're inheriting from dict to extend its behavior, there are a lot of side effects with that, and it's recommended to use https://docs.python.org/3/library/collections.html#collectio... instead.
From right above where you linked to:
> The need for this class has been partially supplanted by the ability to subclass directly from dict; however, this class can be easier to work with because the underlying dictionary is accessible as an attribute.
Sounds like (unless you need the dict as a separate data member) this class is a historical artefact. Unless there's some other issue you know of not mentioned in the documentation?
dict doesn't follow the usual object protocol, and overloaded methods are runtime dependent. It's only guaranteed that non-overloaded methods are resolved least surprisingly.
I think you mean overridden (i.e. defined in both base class and derived class) rather than overloaded (i.e. defined more than once in a single place but with different argument types, as least from a typing point of view [1]). Your comment seriously confused me till I figured that out.
[1] https://typing.python.org/en/latest/spec/overload.html
Even then, to be honest I'm a bit sceptical. Can you point at a link in the official documentation that says overriding methods of dictionaries may not work? I would have thought the link to UserDict would have mentioned that if true. What do you mean they are "runtime dependent"?
2 replies →
No, that is not the recommendation. People routinely and reliably inherit from dict.
The UserDict class is mostly defunct and is only still in the standard library because there were a few existing uses that were hard to replace (such as avoiding base class conflicts in multiple inheritance).
Ah, Python. The language where nobody agrees on the right way to do things, ans just does their own instead. Five ways to describe an object of a certain shape? Six package managers, with incompatible but overlapping ways to publish packages, but half of them without a simple way to update dependencies? Asynchronous versions of everything? Metaprogramming that makes Ruby blush? Yes! All of it! Lovely.
UserDict is not formally deprecated but it will be someday, so code that relies on it is not future-proof.