python-stdlib/collections-defaultdict: Add items() function.

[agatti]

Summary

This PR adds the items() functions to collections.defaultdict, acting as a simple proxy to the underlying dictionary container.

This fixes #350.

The package's version number was bumped up by 0.1.0 since a new function was added to the module.

Testing

The added tests in python-stdlib/collections-defaultdict were run successfully both on CPython (with a tweaked import harness) and on MicroPython's git master.

Trade-offs and Alternatives

This adds 81 bytes to the final module. I'm a bit surprised it took that much, but unless it is documented that the backing dictionary can be accessed via self.d when code runs on MicroPython, I don't see any other safe way to enumerate the contents [1].

Generative AI

I did not use generative AI tools when creating this PR.

---

[1]

This trips up MicroPython, for example:

from collections import defaultdict
a = defaultdict.defaultdict(list)
for i in a:
    print(i)

On current MicroPython's git master:

$ cd python-stdlib/collections-defaultdict
$ $MICROPYTHON
MicroPython v1.28.0-preview.306.g5c00edcee2.dirty on 2026-03-23; linux [GCC 15.2.1] version
Type "help()" for more information.
>>> from collections import defaultdict
>>> a = defaultdict.defaultdict(list)
>>> for i in a:
...     print(i)
...
[]
[]
[]
[]
# `[]` being repeated a fairly large number of times here...
[]
[]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "collections/defaultdict.py", line 20, in __getitem__
MemoryError: memory allocation failed, allocating 260368 bytes
>>>

Whilst this works as expected on CPython 3.14 (and probably earlier versions too):

$ python
Python 3.14.3 (main, Feb 13 2026, 15:31:44) [GCC 15.2.1 20260209] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from collections import defaultdict
>>> a = defaultdict(list)
>>> for i in a:
...     print(i)
... 
>>>

[dpgeorge]

Thanks, that's a nice and simple addition, and definitely useful.

(Eventually it might be good to implement the iterator protocol on this class.)

[dpgeorge]

This adds 81 bytes to the final module

That's strange. I tested it using mpy-cross defaultdict.py to just compile this source file, and see +23 byte change with this PR on the size of defaultdict.mpy. Using mpy-cross -O3 the increase is +19.