[PyQt] SIP newcomer questions/complaints

Kevin Watters kevin at digsby.com
Mon Apr 7 01:11:24 BST 2008

I just started looking into SIP this weekend (I'm trying to wrap the wxWidgets
library--has this been attempted before?), and I had a couple thoughts and

1) The docs make no mention of the fact that you cannot use keyword arguments
when calling C functions. This was a surprising limitation coming from SWIG.

2) The docs for creating and using a Makefile are lacking--I'm not sure how to
get them to work. Do I need a ParentMakefile above the one in my source
directory? Is my source directory the same as my generated source directory?
Admittedly I'm completely in the dark when it comes to make, so I got stuck at

make[1]: *** No rule to make target `sipAPIwx.h', needed by `sipwxcmodule.o'.

This is probably no big deal for most people fluent in with UNIX dev toolchain,
but a simple example with a multi SIP file project might help the rest of us
with this :-)

3) I ended up using the distutils support--which worked great out of the box.
But now my scripts are generating enough time to make the compile-link time
cycle significant. My SIP files use one root file that %Includes all of the
other SIP files so that everything goes into one module.

But when I change one of the sub SIP files, SIP doesn't recognize that its
corresponding files need to be regenerated. So the only way I've found to
recompile is to "touch" the root SIP file, which causes SIP to regen ALL of my
generated cpp files, and subsequent GCC to recompile ALL of them. Is there an
easy solution to this?

4) Since there is no preprocessor support for .sip files, I ended up using
%Feature and %If to enable and disable blocks of code, depending on the
configuration. But it's annoying to have to pass -x FEATURENAME on the
commandline to disable features. Obviously this can be automated, but it might
be better to allow "%Feature On" or "%Feature Off," or to have an option for
SIP to take additional arguments from a file.

5) The grammar for SIP syntax mentions __repr__, but the docs do not. After
some strange compile errors I managed to get a __repr__ to work with the
following code:

 void __repr__(); %MethodCode return PyString_FromFormat("<wx.Size (%d, %d)>",
sipCpp->x, sipCpp->y); %End

Why does the type have to be void?

6) The docs show show no comparisons with similar tools. I'm trying SIP to see
if the memory usage of a large wxPython app can be reduced--I have seen
comparisons claiming that SIP would be slower than hand generated code, but
faster than SWIG. This seems to be a fair assumption, since SWIG generates lots
of Python shadow classes, and SIP does not. But some data, or even anecdotal
advice about what you're going to get out of SIP compared to SWIG might be
useful in the documentation.

Thanks in advance for any help!

- Kevin

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