py_cpp*

The source code for py_cpp, including a MSVC demo project is available here.

Synopsis

py_cpp is a system for quickly and easily interfacing C++ code with Python such that the Python interface is very similar to the C++ interface. It is designed to be minimally intrusive on your C++ design. In most cases, you should not have to alter your C++ classes in any way in order to use them with py_cpp. The system should simply “reflect” your C++ classes and functions into Python. The major features of py_cpp include support for:

• Subclassing extension types in Python
• Overriding virtual functions in Python
• [Member] function Overloading
• Automatic wrapping of numeric operators

Supported Platforms

py_cpp has been tested in the following configurations:

• Against Python 1.5.2 using the following compiler/library:
  • MSVC++6sp4
  • MSVC++6sp4/STLport 4.0
  • GCC 2.95.2 [by Ullrich Koethe]
  • GCC 2.95.2/STLport 4.0
  • Compaq C++ V6.2-024 for Digital UNIX V5.0 Rev. 910 (an EDG-based compiler) with STLport-4.1b3 [by Ralf W. Grosse-Kunstleve]
  • An upcoming release of Metrowerks CodeWarrior Pro6 for Windows (the first release has a bug that's fatal to py_cpp)
  
  
• Against Python 2.0 using the following compiler/library combinations:
  • MSVC++6sp4 [by Alex Martelli]

Py_cpp requires the boost libraries, and is has been accepted for inclusion into the boost libraries pending “boostification“ (completion of the documentation, change in some naming conventions and resolution of some namespace issues).

Credits

• David Abrahams originated and wrote py_cpp.
• Ullrich Koethe had independently developed a similar system. When he discovered py_cpp, he generously contributed countless hours of coding and much insight into improving it. He is responsible for an early version of the support for function overloading and wrote the support for reflecting C++ inheritance relationships. He has helped to improve error-reporting from both Python and C++, and has designed an extremely easy-to-use way of exposing numeric operators, including a way to avoid explicit coercion by means of overloading.
• The members of the boost mailing list and the Python community supplied invaluable early feedback. In particular, Ron Clarke, Mark Evans, Anton Gluck, Ralf W. Grosse-Kunstleve, Prabhu Ramachandran, and Barry Scott took the brave step of trying to use py_cpp while it was still in early stages of development.
• The development of py_cpp wouldn't have been possible without the generous support of Dragon Systems/Lernout and Hauspie, Inc who supported its development as an open-source project.

Table of Contents

1. A Brief Introduction to writing Python extension modules
2. Comparisons between py_cpp and other systems for extending Python
3. A Simple Example Using py_cpp
4. Overridable Virtual Functions
5. Function Overloading
6. Inheritance
7. Special Method and Operator Support
8. A Peek Under the Hood
9. Building a Module with Py_cpp
10. Advanced Topics
    1. class_builder<>
    2. enums
    3. References
    4. Pointers and Smart Pointers
    5. Built-in Python Types
    6. Other Extension Types
    7. Templates

More sophisticated examples are given in extclass_demo.cpp, extclass_demo.h, and test_extclass.py in the source code archive. There's much more here, and much more documentation to come...

Questions should be directed to the boost mailing list.

Naming Contest

Yes, I know py_cpp is a lousy name. Problem is, the best names my puny imagination can muster (IDLE and GRAIL) are taken, so I'm holding a naming contest. First prize? You get to pick the name<0.2wink> and you will be credited in the documentation. Names that have been suggested so far include:

• Py++
• Python++
• Coil
• SnakeSkin
• CCCP - Convert C++ Classes to Python
• C³PO - Convert C++ Classes to Python Objects
• PALIN - Python Augmented-Language INtegration
• CLEESE - C++ Language Extension Environment Supremely Easy
• JONES - Just Obscenely Neat Extension System
• C-thru
• SeamlessC
• BorderCrossing
• Perseus (because he solved a hairy problem involving snakes by using reflection and was invisible most of the time).

© Copyright David Abrahams 2000. Permission to copy, use, modify, sell and distribute this document is granted provided this copyright notice appears in all copies. This document is provided “as is” without express or implied warranty, and with no claim as to its suitability for any purpose.

Updated: Nov 25, 2000