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Re: Help with Python SWIG bindings and callbacks

From: David James <james82_at_gmail.com>
Date: Mon, 25 Aug 2008 19:02:09 -0700

On Mon, Aug 25, 2008 at 6:18 PM, Lawrence Stewart <lstewart_at_room52.net> wrote:
>> Have you considered trying out the new ctypes python bindings? I tried
>> converting your script to use the new ctypes python bindings, and it
>> seems to work fine. See the example below.
>> from csvn.core import *
>> import csvn.wc
>> svn_cmdline_init("", csvn.core.stderr)
>> wc = csvn.wc.WC("wc")
>> def notify_func(obj):
>> if obj.action == svn_wc_notify_update_update:
>> print "U", obj.path
>> elif obj.action == svn_wc_notify_update_completed:
>> print "Completed", obj.path
>> wc.checkout("http://svn.collab.net/repos/svn/trunk/www/")
>> wc.update(revnum=32695)
>> wc.set_notify_func(notify_func)
>> wc.update(revnum=32696)
>> The above example works on my machine, and outputs the following:
>> U wc/faq.ja.html
>> U wc
>> Completed wc
>> The ctypes python bindings are available at
>> http://svn.collab.net/repos/svn/branches/ctypes-python-bindings/, and
>> should work fine with Subversion 1.5.x. Hopefully they will be
>> standard in Subversion 1.6.0, but we are still working on a few
>> finishing touches.
> No I haven't considered ctypes (wasn't even aware of it). Thanks for the
> pointer. Is there other documentation than the README in the top level
> branch dir that I should be referring to?
> Is it anticipated that the ctypes interface will usurp the SWIG code? I had
> kind of hoped to create a script that was backward compatible with vanilla
> SVN back to 1.4.x hence the use of the SWIG API and not something like
> PySVN, but I guess it's not disastrous if that's not the case.
> As a bit of background, I'm trying to create a script that allows me to
> mirror a portion of a remote repo into my own development repo as a vendor
> branch. The existing tools just don't seem to cut it for this use case and
> hacking the svn C code seemed a bit extreme to get something working
> relatively quickly. Given the trouble I'm having with the bindings perhaps I
> should have just dived straight into writing a small C app. I'm willing to
> be told otherwise if someone here has/knows such a tool in which case my
> need for python bindings disappears :)

Hi Lawrence,

The ctypes python bindings should work with vanilla Subversion 1.4.x
or later. I haven't tried them recently with Subversion 1.4, but they
should work. If they don't still work with SVN 1.4, let me know.

One really nice part about the ctypes python bindings is that you
don't need to recompile the bindings for it to work with a different
version of Subversion, or a different platform -- it's a pure python

If you like Python, the ctypes python bindings are probably the
easiest way to get started with the Subversion API. The low level APIs
in ctypes don't have documentation, but they don't need it, because
they are an exact mirror of the C APIs. All C APIs work verbatim
identical in the ctypes python bindings.

We also implemented some higher level python objects which make it
easier to do common tasks in the ctypes python bindings. I find these
quite helpful. You can learn the high level APIs by looking at the
test suite for the ctypes python bindings. If you want examples of how
to use the low level APIs, try taking a look at the implementation of
the low level APIs.

It's certainly possible to get the SWIG bindings working and doing
everything you need, but I find them kind of difficult to use because
you need to do so many workarounds to get them working. The ctypes
python bindings are refreshing in comparison because they work
consistently and reliably, just like the underlying C APis.

Hope this helps,


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Received on 2008-08-26 04:02:29 CEST

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