In older versions of sip (4.7.3), I have used __setitem__, __getitem__ to
access/set elements from multidimensional quantities of a wrapped c++
object that uses operator()(int,int). For example, the following sip code
used to work fine
class A {
int operator()(int x,int y) const;
int __getitem__(int x,int y) const;
%MethodCode
...
%End
void __setitem__(int x,int y, int val) const;
%MethodCode
...
%End
};
>From the ChangeLog this feature seemed to have been removed (in a related
mailing list post, it was reported that the above usage was a bug
http://article.gmane.org/gmane.comp.python.pyqt-pykde/12342/match=sip+__setitem__).
With the new checking (sip 4.7.9, possibly earlier), the above code will
now give an error (e.g., sip: A.sip:18: Incorrect number of arguments to
Python slot). The previous mailing list post
(http://thread.gmane.org/gmane.comp.python.pyqt-pykde/12342) suggested to
either not use __setitem__/__getitem__ for this purpose or to use a tuple.
I updated my code and the tuples work fine for __getitem__, but I cannot
seem to get the tuple to work for __setitem__.
For example,
A.sip:
class A {
int __getitem(int x,int y);
%MethodCode
//This is just a dummy, actually parse the tuple and extract indices...
%End
void __setitem__(SIP_PYOBJECT, SIP_PYOBJECT);
%MethodCode
//Do something here....
%End
};
Python test:
from A import A
a = A(10,10)
# Getting works fine, no error parsing arguments
b = a[0,0]
b = a[0]
# Setting works with anything but tuple
a[0] = 1 # Works fine
a[[1,2]] = 1 # Also works, but is not really a desired syntax
a[0:5] = 1 # Works, would check for this when parsing args.
a[(0,1)] = 1 # Error: "TypeError: too many arguments to A.__setitem__(), 2 at
most expected"
a[0,1] = 1 # Same error
tup = (0,1)
a[tup] = 1 # Same error
The tuple always gets unpacked into more than one argument for __setitem__
and causes the TypeError, which happens before any of the sip %MethodCode
can be called.
Looking at the generated code for the __setitem__, the parsing of args
looks something like:
sipParseArgs(&sipArgsParsed,sipArgs,"P0P0",&a0,&a1)
On the other hand, the parsing of args for __getitem__ seems to work due
to the single arg format of "1P0". Manually editing the generated code to
return the args packed into a single tuple (including the set value) like
__getitem__ works but is not a satisfying solution.
Changing the function signature of __setitem__ to take a SIP_PYTUPLE as
the first argument also does not help, although it does change the
sipParseArgs format to "TP0" (e.g.,
sipParseArgs(&sipArgsParsed,sipArgs,"TP0",&PyTuple_Type,&a0,&a1)). I
suspect this call would succeed if there was a way to make sipParseArgs
put the first n-1 sipArgs into a0 and the last argument into a1.
The parsing of arguments for other methods with similar signature, e.g.,
"void afunc(SIP_PYOBJECT, SIP_PYOBJECT)", does indeed accept stuff like
afunc((1,2), 0), so the problem appears to be with __setitem__.
I could be doing something wrong as no one else appears to be having this
problem. If not, is there a some other way to force the argument parsing
to put the first args into a tuple? Or is there a way to do it by hand
(like a NoArgParser for member functions)? Currently, I modified the
sip source (in sipgen/parser.c:findFunction, line 7642, {"__setitem__",
"setitem_slot, TRUE, -1}) to not check the # of arguments to
__setitem__/__getitem__. For the time being, this gives the behaviour of
the older version, so that I can remain using my old sip files (like the
beginning of this post).
Thanks,
Neil Birkbeck
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