Allow keyword syntax for NamedTuple #321
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| @@ -1985,20 +1987,29 @@ class Employee(NamedTuple): | |||
| The resulting class has one extra attribute: _field_types, | |||
| giving a dict mapping field names to types. (The field names | |||
| are in the _fields attribute, which is part of the namedtuple | |||
| API.) Backward-compatible usage:: | |||
| API.) Alternative equivalent keyword syntax is also accepted:: | |||
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Can you change the earlier part of the docstring (line 1975) to emphasize that the both the PEP 526 syntax and the keyword args syntax are only supported in Python 3.6+? (I can't add github comments that far back.)
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@gvanrossum Note that this docstring will be seen only by people who use Python 3.6+, this docstring is inside a big if sys.version_info[:2] >= (3, 6): above. Anyway, I updated the docstring to cover this and next comment.
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@gvanrossum OK, now there is no big if sys.version_info[:2] >= (3, 6):, there is the same code and docstring for all versions.
| def __new__(self, typename, fields): | ||
| def __new__(self, typename, fields=None, **kwargs): | ||
| if fields is None: | ||
| fields = kwargs.items() |
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This should be disallowed for Python <= 3.5. (Remember that this code will be in the "typing" package which should work for Python 3.2 and up, and it will be copied verbatim into the 3.5 branch as well.)
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@gvanrossum This code is also inside if sys.version_info[:2] >= (3, 6): I mentioned above. So that the else: branch is used for other versions, and both keyword and class syntax fail with a TypeError.
I will add a new commit now, where I will "unify" the code, this will give better error messages.
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| Employee = NamedTuple('Employee', name=str, id=int) | ||
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| Backward-compatible usage:: |
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So "backward-compatible" sounds a bit pejorative. I think this should just be referred to as the way to do it for Python versions <= 3.5.
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FWIW I'm fine with having this in 3.6 without supporting it in mypy. Once 3.6 is released we can't change typing.py easily (not until 3.6.1 anyways) but we can add support to mypy at any time. |
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@gvanrossum Thank you for review! I have implemented your comments. and Please take a look! |
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@gvanrossum Does this look OK now? |
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OK. Another leap of faith. :-) Did you have other changes to typing.py? Or can I do the final merge into CPython and mypy now? |
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@gvanrossum Thanks! :-)
There is #322 , but note that mypy support for |
Fixes #302
@gvanrossum Here is a simple implementation for keyword syntax that you proposed:
Note that this requires 3.6+ since order of kwargs should be preserved.