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Fix _csv.Dialect.__init__ #12320

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merged 7 commits into from
Oct 3, 2024
Merged

Fix _csv.Dialect.__init__ #12320

merged 7 commits into from
Oct 3, 2024

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sobolevn
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@sobolevn sobolevn commented Jul 11, 2024 •
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All props can be passed to __init__ as pos-or-keyword:

>>> _csv.Dialect(1)
<_csv.Dialect object at 0x106604d70>
>>> _csv.Dialect(dialect=1)
<_csv.Dialect object at 0x106605d90>

>>> _csv.Dialect(delimiter='.')
<_csv.Dialect object at 0x106605790>

>>> _csv.Dialect(quotechar='.')
<_csv.Dialect object at 0x106605970>
>>> _csv.Dialect(quotechar=None)
<_csv.Dialect object at 0x106605850>

Source: https://github.com/python/cpython/blame/e6264b44dc7221c713b14dfa0f5929b33d362829/Modules/_csv.c#L389

sobolevn and others added 2 commits July 11, 2024 12:59
@sobolevn
Fix _csv.Dialect.__init__
f6d4a44 
All props can be passed to `__init__` as pos-or-keyword:

```python
>>> _csv.Dialect(1)
<_csv.Dialect object at 0x106604d70>
>>> _csv.Dialect(dialect=1)
<_csv.Dialect object at 0x106605d90>

>>> _csv.Dialect(delimiter='.')
<_csv.Dialect object at 0x106605790>

>>> _csv.Dialect(quotechar='.')
<_csv.Dialect object at 0x106605970>
>>> _csv.Dialect(quotechar=None)
<_csv.Dialect object at 0x106605850>
```
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@sobolevn
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Ok, I see: # actually csv.Dialect is a different class to _csv.Dialect at runtime, but for typing purposes, they're identical

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srittau commented Jul 11, 2024 •
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See #3613 for why this was added. csv.Dialect looks to be a weird hack at runtime, probably back from a time when C classes couldn't be sub-classed by Python code.

@JelleZijlstra
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Do you still want to change anything here? CI is failing.

@sobolevn
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sobolevn commented Oct 3, 2024

We want:

  • "Base class" _csv.Dialect must have __init__ with parameters
  • "Child class" csv.Dialect must have __init__(self)

I can make csv.Dialect a subclass of _csv.Dialect and make unsafe __init__ redefinition with type ignores. Will try that :)

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sobolevn commented Oct 3, 2024

@JelleZijlstra thanks for the reminder!

srittau
srittau reviewed Oct 3, 2024
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stdlib/_csv.pyi
def __init__(self) -> None: ...

_DialectLike: TypeAlias = str | Dialect | type[Dialect]
def __init__(
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Shouldn't this be __new__?

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It is __new__ for _csv.Dialect, but __init__ for csv.Dialect. I feel safer to use __init__ in both cases.

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github-actions bot commented Oct 3, 2024

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

@srittau srittau merged commit d16fe74 into main Oct 3, 2024
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@srittau srittau deleted the sobolevn-patch-1 branch October 3, 2024 09:33
@tungol tungol mentioned this pull request Oct 14, 2024
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3 participants
@sobolevn @srittau @JelleZijlstra