New submission from Andrew Barnert:
None of the below are very serious or likely to mislead anyone using or
implementing Python, but...
---
3.3.2. Customizing attribute access
The docs for `__dir__` say:
> A sequence must be returned. dir() converts the returned sequence to a list
> and sorts it.
At least in CPython and PyPy, this isn't enforced; any iterable can be returned
(and it's then converted to a list and sorted). You can even make `__dir__` a
generator function. (I've never seen that in the wild--but I have seen code
that returns a `map` iterator.)
I think it would be better to say "An iterable must be returned. dir() converts
the returned iterable to a list and sorts it."
---
3.3.2.3. __slots__
> This class variable can be assigned a string, iterable, or sequence of
> strings...
While it's true that you can assign any iterable, it's at best misleading to
assign an iterator. For example, if you use `__slots__ = iter('abc')`, you will
get a class with descriptors named `a`, `b`, and `c`, but with an empty
iterator in `__slots__`. There's probably no reason to actually outlaw that,
but it might be worth noting in 3.3.2.3.1 along with the other weird
possibilities like assigning a mapping.
---
3.3.6. Emulating container types
The docs still say that the ABCs are in `collections` rather than
`collections.abc`.
> ... for mappings, __iter__() should be the same as keys()
No; `__iter__()` should be an iterator over the keys; `keys()` _can_ be an
iterator, but generally should be a view instead.
> The membership test operators (in and not in) are normally implemented as an
> iteration through a sequence. However, container objects can supply the
> following special method with a more efficient implementation, which also
> does not require the object be a sequence.
I don't think this should say "through a sequence". They're implemented as
iteration through whatever the container is, whether it's a sequence, a set, a
linked list, or anything else. The documentation on `__contains__` immediately
below clarifies this, but it's probably better to be clear from the start.
----------
assignee: docs@python
components: Documentation
messages: 256445
nosy: abarnert, docs@python
priority: normal
severity: normal
status: open
title: Reference 3. Data Model: miscellaneous minor cleanups on the word
"sequence".
type: enhancement
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue25866>
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