Hi,
(Sent to both cython-devel and cython-users. However, I'm not subscribed
to users I think, so please forward if it doesn't reach there).
On closer inspection I believe both are following Python behaviour (and
thus behaving correctly). In Python any
`__name_preceded_by_double_underscores` used within a class ends up
looking up `_Classname__name_preceded_by_double_underscores`. Therefore
in case 1 it's looking up `_Bar__foo` and not finding it.
Therefore, I think it is the "correct" thing to do.
This proved a pain with the `__pyx_unpickle` functions that Cython
generates. In the end I just disabled it for `__pyx_` names, which I
guess could be called hypocrisy .
David
On 23/04/2020 18:47, Stefan Behnel wrote:
Hi,
thanks for the very detailed report.
I'm CC-ing cython-devel, but let's keep the discussion for this on the
cython-users list.
The background here is Github issue 1382 and PR 3123
https://github.com/cython/cython/issues/1382
https://github.com/cython/cython/pull/3123
This was newly merged for alpha 2, and I consider it somewhat provisional.
It makes "private" Python names follow Python semantics, but if that poses
excessive breakage for existing code, then we'll have to find a pragmatic
way to deal with it.
'Toni Barth' via cython-users schrieb am 23.04.20 um 19:07:
I just updated Cython from 3.0a1 to 3.0a2 in one of my projects and
noticed that it seems to introduce issues with private
functions/methods, means methods with leading __.
I noticed two cases which now fail in my project. I'm however unsure if
thats supposed to happen or if its a problem with the new Cython build.
Case 1: private function not declared
crash.pxd:
cpdef __foo()
cdef class Bar:
cpdef run(Bar self)
crash.pyx:
cpdef __foo():
print("foo")
cdef class Bar:
cpdef run(Bar self):
__foo()
print("bar")
Running this with the following command:
py -3 -c "import pyximport;pyximport.install();import
crash;crash.Bar().run()"
Result:
crash.c
C:\Program Files (x86)\Microsoft Visual
Studio\Shared\Python36_64\lib\site-packages\Cython\Compiler\Main.py:344:
FutureWarning: Cython directive 'language_level' not set, using '3str'
for now (Py3). This has changed from earlier releases! File:
D:\crash\crash.pxd
tree = Parsing.p_module(s, pxd, full_module_name)
Error compiling Cython file:
------------------------------------------------------------
...
cpdef __foo():
print("foo")
cdef class Bar:
cpdef run(Bar self):
__foo()
^
------------------------------------------------------------
crash.pyx:6:4: undeclared name not builtin: __foo
At least this looks like a bug to me. Global module names should not be
impacted by this change.
Error compiling Cython file:
------------------------------------------------------------
...
cpdef __foo():
print("foo")
cdef class Bar:
cpdef run(Bar self):
__foo()
^
------------------------------------------------------------
crash.pyx:6:4: '__foo' redeclared
Error compiling Cython file:
------------------------------------------------------------
...
cpdef __foo()
^
------------------------------------------------------------
crash.pxd:1:12: Previous declaration is here
Lovely :)
Another problem, probably related, occurs when trying to override a
private method in a derived class:
Case 2: overriding private class methods
base.pxd:
cdef class Base:
cdef void __foo(Base self)
cpdef run(Base self)
base.pyx:
cdef class Base:
cdef void __foo(Base self):
print("foo!")
cpdef run(Base self):
self.__foo()
extend.pxd:
from base cimport Base
cdef class Extend(Base):
pass
extend.pyx:
cdef class Extend(Base):
cdef void __foo(Extend self):
print("bar")
Running with the following command:
py -3 -c "import pyximport;pyximport.install();import
extend;extend.Extend().run()"
Results in the following output:
extend.c
C:\Program Files (x86)\Microsoft Visual
Studio\Shared\Python36_64\lib\site-packages\Cython\Compiler\Main.py:344:
FutureWarning: Cython directive 'language_level' not set, using '3str'
for now (Py3). This has changed from earlier releases! File:
D:\crash\extend.pxd
tree = Parsing.p_module(s, pxd, full_module_name)
Error compiling Cython file:
------------------------------------------------------------
...
cdef class Extend(Base):
cdef void __foo(Extend self):
^
------------------------------------------------------------
extend.pyx:3:7: C method '_Extend__foo' not previously declared in
definition part of extension type 'Extend'
This, OTOH, is intended. Private methods are not meant to be inherited and
overridden. That's what makes them "private" :) That's consistent with
Python semantics.
I think it's somewhat up for debate if this should apply in the same way to
cdef classes as for Python classes. But from a language design point of
view, having this kind of difference between the two seems a bad idea.
Do you feel like argueing against this? :)
Stefan
_______________________________________________
cython-devel mailing list
cython-devel@python.org
https://mail.python.org/mailman/listinfo/cython-devel
_______________________________________________
cython-devel mailing list
cython-devel@python.org
https://mail.python.org/mailman/listinfo/cython-devel
