Remove usage of UserDict

[Thijs Triemstra]

Remove usage of UserDict once Python 2.6 support is dropped completely (or manhole.explorer or protocols.postfix are ported to python 3).

twisted/protocols/postfix.py:import UserDict
twisted/protocols/postfix.py: UserDict.UserDict):
twisted/manhole/explorer.py:import UserDict
twisted/manhole/explorer.py:class Pool(UserDict.UserDict):

[therve]

Note that UserDict isn't in the collections module in 2.X. Regarding DictMixin, you should be able to use MutableMapping with some adjustement.

[Thijs Triemstra]

Meh, not sure why I didnt notice that before. So in Python 2.7 it's in the old place and Python 3 moves it to the collections module. I suggest to add a twisted.python.compat version in that case like we did with execfile.

[Antoine Pitrou]

In many cases, UserDict is replaceable with dict, which is better than importing some crufty compatibility code. I would suggest trying each case separately.

[Vladimir Perić]

Remove UserDict

[Vladimir Perić]

Attached patch takes care of UserDict, by inheriting directly from dict. It's a very small patch, but this is kinda low-level so smaller is better; I'm going to open a separate ticket for replacing DictMixin with MutableMapping (I almost have a patch, but it's a different change again and smaller is better). The changes here should be ok - all the touched lines are tested and all tests pass.

In lieu of what this ticket actually does, I'll change the summary to just "Remove usage of UserDict"

[Thijs Triemstra]

Thanks for working on this. Most changes are indeed covered by tests.

• twisted.protocols.postfix the docstring """A dict that preserves insert order whenever possible.""" should be on 3 lines
• Same for """A dict that preserves insert order whenever possible.""" in twisted.python.util
• It's missing a .removal newsfile
• There are 3 lines not covered for OrderedDict and since you're changing it's class it would be good to have tests for those lines (copy and iterkeys) as well for peace of mind.

Can you put the patch in a branch as well so we can buildbot test it?

[Vladimir Perić]

1, 2: will do 3: Why .removal? No features are getting removed here, I wouldn't give it more than a .misc personally. 4: Ah, I really don't feel like doing this, in part because those tests themselves probably also need cleanup and I don't feel like doing that. As it stands, all the changes *are* tested and the ticket does what it says it does. Still, if you want to insist on this, I guess I'll have to do it. :)

[Thijs Triemstra]

• during the python 3 port (r36719) OrderedDict in python.util changed it's base class from UserDict to object for python 3 only.
• usage of DictMixin in http_headers was removed during the python 3 port.
• the following classes still use UserDict (excluding python.util):

  twisted/protocols/postfix.py:import UserDict
  twisted/protocols/postfix.py: UserDict.UserDict):
  twisted/manhole/explorer.py:import UserDict
  twisted/manhole/explorer.py:class Pool(UserDict.UserDict):
  

I suggest we remove usage of UserDict once Python 2.6 support is dropped or python 3 support is added for manhole.explorer or protocols.postfix. Updating the ticket description and priority.

[Adi Roiban]

(In [46232]) Branching to userdict-removal-5789.

[Adi Roiban]

Hi,

Many thanks for the patch!

We can not just remove True and False from twisted/manhole/explorer.py as they are public. If you want to get rid of them, they will need to go to a deprecation first.

I have reverted those changes.

---

Pool.data was a public member. We can not remove it without a deprecation as code using Pool() instanced as UserDict will break.

I have committed an example of deprecating the data attribute.

Deprecation policy is explained here https://twistedmatrix.com/trac/wiki/CompatibilityPolicy

Here is a update of the policy with awaits review

​https://github.com/twisted/twisted/compare/trunk...deprecation-docs-8082

---

I know that this is a minor change, but we made a compatibility promise to our users.

If you think that this need an exception, please ask for exception approval over the mailing list.

Please update the patch to deprecate the attributes removed together with the removal of UserDict and add tests for the deprecations.

Thanks!

[Craig Rodrigues]

twisted.manhole is gone. UserDict is only used in twisted.protocols.postfix. On Python 3, it is imported from collections.