The staticmethod constructor is useful I think - regular constructors
can't take C/C++ types so the static method constructor provides a means
of doing something like:
cdef mycppclass inst = # some call to cpp
return wrapperclass.create(inst)
I definitely agree you want some means of naming the generated class. At
the minute I'm my thoughts are to do two things:
1. Having a cache of the generated classes (so autowrap[S] always
returns the exact same class if you've already created one). That'd mean
there's no penalty for just always referring to it as autowrap[S], so
you don't /really/ need to name it.
2. Allow something like `ctypedef autowrap[S] whatever_name` (which
doesn't currently look to work...)
With that said, adding an option to override the name would be pretty
easy, and probably useful.
As always, it's a fine balance is always between making sure you have
the useful options and ending up in a huge option overload so no-one can
work out where to start.
On 13/03/2020 11:29, Schlimbach, Frank wrote:
Right. Sorry, not sure what I was thinking.
Instead of a staticmethod constructor, maybe it's more useful to have a keyword
arg for the name of the generated extension class?
-----Original Message-----
From: cython-devel <cython-devel-bounces+frank.schlimbach=intel....@python.org>
On Behalf Of da-woods
Sent: Friday, March 13, 2020 12:02 PM
To: cython-devel@python.org
Subject: Re: [Cython] Auto-generation of wrapper types
(Sorry, originally replied just to Frank not to the list)
If I understand you correctly it'd be something like:
cdef class WrappingOfS(autowrap[S]):
def new_method(self):
# implementation
i.e. if you want to do something the automation can't do then you just inherit.
If I don't understand you correctly then please clarify...
On 13/03/2020 09:56, Schlimbach, Frank wrote:
I like automatism, this one looks useful.
How would you allow extending the Extension type with a new attribute or
method? I'd expect that in many cases you need to do more than just wrapping
the C class/struct.
-----Original Message-----
From: cython-devel
<cython-devel-bounces+frank.schlimbach=intel....@python.org> On Behalf
Of da-woods
Sent: Thursday, March 12, 2020 4:12 PM
To: cython-devel@python.org
Subject: [Cython] Auto-generation of wrapper types
The process of wrapping a C struct or C++ class in an extension type often has
the user doing a pretty mechanical duplication of attributes/functions that
Cython already knows about. I'm looking at doing:
cdef struct S:
int a
# etc.
then `cython.autowrap[S]` would create an extension type that wraps S by value.
All attributes convertible to/from a Python type gets a property (as well as
any attribute that has an has an autowrap declared). For `cppclass` this would
extend to member functions as well - this obviously gets more involved, but
again the same basic rule applies of only including stuff with an obvious
conversion.
I wouldn't propose to deal with the C++ nightmare of "how to return an owned
reference". The idea would be to copy by value or nothing.
I'd also propose only minor customization via keyword arguments (for example the name of
a cdef staticmethod constructor, the name of the "obj" field in the C++ class).
The basic rule would be that if it doesn't do what you want then it's an extension type,
so you can always inherit from it and define the missing bits.
Obviously structs have already have an automatic conversion to/from dicts and
some cppclasses have autoconversions too. This wouldn't aim to replace that -
it'd just be an option that the user could explicitly ask for.
I have a somewhat working prototype for the struct side. Obviously the real
complications are on the C++ side, but I don't think it's hugely difficult
providing you accept there's lots of stuff that can't be guessed and
inheritance is the way round that.
Does this sound reasonable/something that'd be accepted? Any other thoughts?
David
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Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Gary Kershaw
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
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