Mailman 3 November 1999 - Cplusplus-sig

RE: [C++-SIG] Python calling C++ issues
by Dror, Ephi Dec. 3, 1999

Dec. 3, 1999

Hi Mark, Thanks a lot again. We tried it but unfortunately it did not help in our case. Does anyone know where can we download C++ based debug version of Python 1.52 for Linux? Our next step is to use Python 1.52 which is compiled with C++ and possibly a debug version and then try our little sample. Thanks a lot. Ephi. -----Original Message----- From: Mark Hammond [mailto:mhammond@skippinet.com.au] Sent: Wednesday, November 24, 1999 12:53 AM To: 'Ephi Dror'; c++-sig(a)python.org Subject: RE: [C++-SIG] Python calling C++ issues > Unfortunately, we don't seems to understand what do you mean > by "Object". Is > it something we need to define or is it already defined in a > h file that we > forgot to include. We use Linux/gcc environment. Sorry - I meant "PyObject" > Also, in our sample, we did not use virtual function Hmmm - OK - my advice could well be wrong. Unless your C compiler always adds a vfptr. I have seen this problem (when using virtuals) before and the symptoms sound almost identical. Try the code snippet I posted, and see if the debugger does show the "PyObject *" and the "Spam *" as different values, even though they are pointing to the same object. Otherwise Im afraid I have no idea... Mark. _______________________________________________ C++-SIG maillist - C++-SIG(a)python.org http://www.python.org/mailman/listinfo/c++-sig

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Python calling C++ issues
by Ephi Dror Nov. 24, 1999

Nov. 24, 1999

Hi All, We are exploring the possibility of using Python with conjunction with C++. I recently posted the "Beginner Question" and would like to thank all of you for the great discussion and support we have received. We have managed to make great progress however we run into couple of very strange problems which I would like to bring up here and share them with the group. Any help in solving these issues will be highly appreciated and beneficiary for all. We also think that the attached example could be good starting point for beginners to understand the concept of calling C++ objects from Python. The example contains a simple C++ class with two data members and we have a simple python script which uses the class. The two problems are: 1. The value of the first data member in the class is ok in the constructor, but in all the rest of the member functions it added 2 to the first data member. 2. When we call the destructor, It is executing the destructor, but we get "Segmentation fault" after it finished to execute the python script that calls the functions that call c++ functions. Here is general information on: 1. We use Linux version 6.1 from redhat. 2. We use gcc version egcs-2.91.66 from redhat. 3. we use Python version 1.5.2 compiled with same gcc from redhat. 4. The class files are: spam.cpp and spam.h . 5. The files that include the c functions that wrap the class functions are : c_spam.cpp and c_spam.h . 6. The file that has the module extension is : ext_spam.cpp. 7. The file that includes the Python script that call the c++ is run. We suspect that the problems might be one or combination of the following issues: 2. Makefile bug (C++ flags and/or shared lib flags are missing). 3. Incompatibility between the way python was built and the version of GCC/C++ we use for the example. Thanks a lot in advance for your cooperation , Cheers, Ephi.

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Controlling python execution from C
by Marcelo Kallmann Nov. 17, 1999

Nov. 17, 1999

Hello, Looking at the manuals, I saw that the function Py_NewInterpreter(), "simulates" the creation of a new thread, so that different scripts would be interpreted "pratically" in paralell by interpreting some bytecodes of each one from time to time. There is even a method to say how many bytecodes to interpret in one script (default=10) before changing to interpret the next script. I tryed to test this feature from C calls, by playing with thread states, interpreter states, run_string, etc, but with no success... What I would like to do is to have n scripts ( char *script[n]; ), and be able to run them in the same application loop, having something like : while ( true ) { for ( int i=0; i<n; i++ ) { restore_python_thread_state ( i ); // would call python functions to restore internal states, etc. run_some_bytecodes_of_python_script ( script[i] ); // would not block my loop, would not run all the script ! } .... } So, first of all, my question is : Is this possible to do ? If so, can someone explain me, or send me some example code please. Thank you all, Marcelo K. LIG - EPFL

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Beginer questions
by Ephi Dror Nov. 15, 1999

Nov. 15, 1999

Hi All, I am a beginner in Python and kind of confused on the subject of combining C++ and Python. I understand that there are 2 ways of interaction. We in our project are only interesting in the case that you call C++ classes and functions from Python, We would like to use C++ classes that are already written in C++ from Python script. We successfully built a shared library with C api, import it and call the function from Python, but when it comes to calling C++, we are completely in the dark and would appreciate any help in that area. Once we understand the subject we would be glad to help other to come up to speed as well. Here is our questions: 1. At this point we are trying to wrap the C++ class as C, but our problem is, how do we pass a pointer from Python to C++ so we can keep the pointer to the class. 2. Is there any easer way to call the functions of C++ classes from python instead of wrapping them with C functions. 3. We recently came across CObject Python object. is it the solution to pass pointer to C function from Python. Is there any example available on this? 4. About Swig. Is swig the best solution for calling C++ from Python. Thanks a lot in advanced for any information which can shade some light on this subject. Ephi.

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WEB DATABASE PROGRAMMER POSITION AVAILABLE
by David Winsen Nov. 9, 1999

Nov. 9, 1999

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