Embedding Python question.

[Thomas Troeger]

Dear all,

I've successfully embedded the Python interpreter into a set of C/C++
application programs that use a larger library project with information
from http://docs.python.org/api/api.html and
http://docs.python.org/ext/ext.html. Now I want to wrap classes and
functions from the associated libraries so that I can write new
applications completely in Python, but I'm not entirely sure how to
start because I have some problems understanding which is the best way.
It would be nice if someone could answer the following questions and
clarify this matter:

- until now I've used the approach as documented in
http://docs.python.org/ext/extending-with-embedding.html to extend the
embedded interpreter and that works pretty well. I'd like to use a
similar approach for other C applications. Can I write a C library that
implements this technique and link it into all C applications that need
Python support, or is there a better, more elegant way?

- in the documentation, there's an example that illustrates the creation
of a python module for pure extending of a python script (the Noddy
stuff). Do I have to make a separate module for each library I want to
wrap? If yes, how can I manage the case where two libraries can access
each other?

- if I write an extension module, how can I handle the case where the C
wrapper methods want to call back into the same Python interpreter instance?

- I think my questions break down into a reference to documentation
where a similar problem is explained in detail. Does anyone have such
information?

Thanks!
Thomas.

 

[Gabriel Genellina]

En Tue, 20 May 2008 06:35:23 -0300, Thomas Troeger

I've successfully embedded the Python interpreter into a set of C/C++
application programs that use a larger library project with information
from http://docs.python.org/api/api.html and
http://docs.python.org/ext/ext.html. Now I want to wrap classes and
functions from the associated libraries so that I can write new
applications completely in Python, but I'm not entirely sure how to
start because I have some problems understanding which is the best way.
It would be nice if someone could answer the following questions and
clarify this matter:

- until now I've used the approach as documented in
http://docs.python.org/ext/extending-with-embedding.html to extend the
embedded interpreter and that works pretty well. I'd like to use a
similar approach for other C applications. Can I write a C library that
implements this technique and link it into all C applications that need
Python support, or is there a better, more elegant way?

(I don't get what you mean by "this technique" and how would you write a
library)

- in the documentation, there's an example that illustrates the creation
of a python module for pure extending of a python script (the Noddy
stuff). Do I have to make a separate module for each library I want to
wrap? If yes, how can I manage the case where two libraries can access
each other?

Normally, yes, you'd write a wrapping module for each library. If both
access each other - well, you'd manage it the same way as you would do it
in C; you're just providing an interfase for calling the functions from
Python. (Hmm, maybe I have an "imagination crisis" today?)

- if I write an extension module, how can I handle the case where the C
wrapper methods want to call back into the same Python interpreter
instance?

I think there is no problem - unless your program is multithreaded, then
you should not release the GIL when calling into your extension if there
is a chance the C code may call Python code.