Joao S. O. Bueno wrote: > There is no need for a whole new syntax for what can trivially be > accomplished by a decorator, > and a simple one, in this cases. > I for one am all for the inclusion of a decorator targeting either the > __init__ method > or the class itself to perform this binding of known arguments to instance > attributes > prior to entering __init__. It could live either in functools or > dataclasses itself. > On Sat, Apr 16, 2022 at 5:49 PM Pablo Alcain pabloalc...@gmail.com wrote: > > The problem of assigning init arguments as attributes has appeared several > > times in the past ( > > https://mail.python.org/archives/list/python-ideas@python.org/message/VLI3DO... > > was the most recent we could find) and is already handled in dataclasses. > > Lately, discussing this topic with a friend, we thought that using a > > specific token could be a possible approach, so you could do: > > class MyClass: > > def __init__(self, @a, @b, c): > > > > pass > > > > > > and it would be analogous to doing: > > class MyClass: > > def __init__(self, a, b, c): > > > > self.a = a > > > > self.b = b > > > > > > Then, you would instantiate the class as usual, and the variables tagged > > with `@` would be bound to the object: > > objekt = MyClass(2, 3, 4) > > print(objekt.b) > > 3 > > print(objekt.c) > > AttributeError: 'MyClass' object has no attribute 'c' > > We have a working implementation here if anyone wants to take a look at: > > https://github.com/pabloalcain/cpython/tree/feature/auto_attribute. Keep > > in mind that we have limited knowledge about how to modify cpython itself, > > and which would the best places be to do the modifications, so it's more > > than likely that some design decisions aren't very sound ( > > https://devguide.python.org/grammar/ and > > https://devguide.python.org/parser/ were incredibly helpful). > > Besides the implementation, we would like to know what the community > > thinks on whether this might have any value. While developing this, we > > realized that Crystal already has this feature (eg > > https://github.com/askn/crystal-by-example/blob/master/struct/struct.cr) > > with the same syntax; which is kind of expected, considering it's syntax is > > based on Ruby. > > Random collection of thoughts: > > > > If auto-assignment made sense in general, one of the reasons we went > > > > for this rather than the decorator approach is that we wouldn't like to > > have a list of strings that can vary decoupled from the actual argument > > name. > > > > The current implementation of `@` works for any function, not only > > > > init. We don't know if this would actually be a desirable feature. > > > > It also works with any function in the wild. This mostly allows for > > > > monkey-patching to work out of the box: > > class Klass: > > ... def __init__(self): > > ... pass > > ... > > def add_parameter(k, @p): > > ... pass > > ... > > Klass.add_parameter = add_parameter > > objekt = Klass() > > print(objekt.p) > > Traceback (most recent call last): > > File "<stdin>", line 1, in <module> > > AttributeError: 'Klass' object has no attribute 'p' > > objekt.add_parameter(11) > > print(objekt.p) > > 11 > > Again, we are not sure if this is desirable, but it's what made most sense > > for us at the moment. > > > > Adding the `@` token to the argument doesn’t remove the variable from > > > > the function/method scope, so this would be perfectly valid: > > def my_function(k, @parameter): > > ... print(parameter) > > my_function(objekt, 4) > > 4 > > k.parameter > > 4 > > > > We didn’t implement it for lambda functions. > > > > Cheers, > > Pablo and Quimey > > > > Python-ideas mailing list -- python-ideas@python.org > > To unsubscribe send an email to python-ideas-le...@python.org > > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > > Message archived at > > https://mail.python.org/archives/list/python-ideas@python.org/message/SCXHEW... > > Code of Conduct: http://python.org/psf/codeofconduct/ > > I had already used this small library in the past, https://pypi.org/project/initify/ , based on a decorator. May be it could be useful for your needs, without adding `@`token to a parameter ?
Yves _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/UYTDOF4O6NCETVYD2DAELD3QUPDPWPEK/ Code of Conduct: http://python.org/psf/codeofconduct/
