[C++-sig] pybindgen: Why do wrapped C++ containers not look more like python containers?

[Gustavo Carneiro]

2009/6/7 Taner Yildirim <taner at seas.upenn.edu>

>  Dear Gustavo,
>
>
>
> Thanks for the detailed explanation, which fixed the problem!. As I
> indicated in my previous email, I am mainly a Fortran programmer and do not
> have much experience with c++. I used to wrap my programs with F2Py but then
>  decided to do right thing and learn c/c++ and rewrite some of the
> applications.  Thanks to your pybindgen code, the wrapping them for python
> would be the easiest part!!
>
>
>
> Back to pybindgen containers, I noticed a strange behavior. I did not check
> the bug reports. Sorry if this was already reported.
>
> I have the following code:
>
>
>
>         mod=Module('tst1')
>
>         mod.add_include('"tst1.h"')
>
>         mod.add_container('std::vector<int>', 'int',
> 'vector',custom_name="std_vec_int")
>
>
>
> In python, I do this:
>
>
>
> A=std_vec_int([1,2,3])
>
> B=std_vec_int([1,2,3])
>
>
>
> But then
>
> A==B  returns false???
>
>
>
> Similarly, I do c=std_vec_int(a) and then check a==c which returns false!!!
>

Type comparison, like many other things, is not yet implemented in
pybindgen.

Like I said, you can do a lot of things by simply "casting" in python to a
list, i.e. instead of:

  A=std_vec_int([1,2,3])

do:

  A=list(std_vec_int([1,2,3]))

It's an ugly workaround but it works ok (although the performance isn't
great).

>
>
> If I do list(A) and list(B), I get the right list. It looks like “==” not
> working or I am again missing something very trivial!
>
You are not missing anything, it's just not implemented.  Unfortunately
Python 2.x has some default comparison function; this is fixed in Python
3.x, which just raises an exception if the comparison operation is not
implemented.


> By the way, this observation is based on pybindgen-0.10.0 and mingw (gcc
> 4.4.0).
>
>
>
> Best regards
>
> Taner
>
>
>
>
> ********************************************************************************
> Dr. Taner Yildirim, Ph.D. Physicist,
> Adjunct Associate Professor,
> Materials Science and Engineering,
> University of Pennsylvania
> and
> Computational and Neutron Science Team Leader,
> NIST Center for Neutron Research,
> National Institute of Standards and Technology,
> 100 Bureau Drive, Gaithersburg, MD 20899-6100.
> Email: taner at nist.gov or taner at seas.upenn.edu
> PHONE: 301-975-6228 FAX : 301-921-9847
> Web : http://webster.ncnr.nist.gov/staff/taner
>
> ********************************************************************************
>
>
>



-- 
Gustavo J. A. M. Carneiro
INESC Porto, Telecommunications and Multimedia Unit
"The universe is always one step beyond logic." -- Frank Herbert
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