Thinking Hybrid - Python/C++ Integration

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Talk given at the January 2008 meeting of the New Zealand Python User Group in Auckland. …

Talk given at the January 2008 meeting of the New Zealand Python User Group in Auckland.
Outline: Talk on integrating native C++ sensibly into Python for ease of use of the code base. Inheriting from C++ classes, overriding functionality, automatically generating the bindings using Py++ and SCons.
Code demonstrated in the presentation can be found here:
http://www.kloss-familie.de/moin/TalksPresentations

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  • 1. Python Extending/Integrating A Real World Example Tips Summary Python where we can, C++ where we must Source: http://xkcd.com/353/ Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 1/25
  • 2. Python Extending/Integrating A Real World Example Tips Summary Thinking Hybrid – Python/C++ Integration (Python where we can, C++ where we must∗ ) Guy K. Kloss New Zealand Python User Group Meeting Auckland, 30 January 2008 ∗ Quote: Alex Martelli, Senior Google Developer Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 2/25
  • 3. Python Extending/Integrating A Real World Example Tips Summary Outline 1 Python 2 Extending/Integrating 3 A Real World Example 4 Tips Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 3/25
  • 4. Python Extending/Integrating A Real World Example Tips Summary Outline 1 Python 2 Extending/Integrating 3 A Real World Example 4 Tips Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 4/25
  • 5. Python Extending/Integrating A Real World Example Tips Summary Why Python? We all know why . . . Some reasons that are important for us: Dynamic High-level data types Embeddable/Mixable Extend Python with components written in C++, Java, C Embed Python into your application and call it from C/C++ Platform independent 50 % less code, 300 % more productive Automatic memory management All those utilities, modules, . . . Many, many more reasons . . . Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 5/25
  • 6. Python Extending/Integrating A Real World Example Tips Summary Why Python? Source: http://xkcd.com/371/ Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 6/25
  • 7. Python Extending/Integrating A Real World Example Tips Summary Outline 1 Python 2 Extending/Integrating 3 A Real World Example 4 Tips Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 7/25
  • 8. Python Extending/Integrating A Real World Example Tips Summary What if I could . . . Use this code more effectively . . . ? [NaSt2D demonstration (native executable)] Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 8/25
  • 9. Python Extending/Integrating A Real World Example Tips Summary Extending/Integration The Contestants: The “classic way” . . . Extending and Embedding the Python Interpreter The “new way” . . . Python ctypes SWIG Boost.Python Others: SIP Pythonizer SILOON (Pyrex) Extensions also for Java, C#, Fortran, . . . available Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 9/25
  • 10. Python Extending/Integrating A Real World Example Tips Summary Extending/Integration The Contestants: The “classic way” . . . Extending and Embedding the Python Interpreter The “new way” . . . Python ctypes SWIG Boost.Python Others: SIP Pythonizer SILOON (Pyrex) Extensions also for Java, C#, Fortran, . . . available Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 9/25
  • 11. Python Extending/Integrating A Real World Example Tips Summary Extending/Integration The Contestants: The “classic way” . . . Extending and Embedding the Python Interpreter The “new way” . . . Python ctypes SWIG Boost.Python Others: SIP Pythonizer SILOON (Pyrex) Extensions also for Java, C#, Fortran, . . . available Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 9/25
  • 12. Python Extending/Integrating A Real World Example Tips Summary Extending/Integration The Contestants: The “classic way” . . . Extending and Embedding the Python Interpreter The “new way” . . . Python ctypes SWIG Boost.Python Others: SIP Pythonizer SILOON (Pyrex) Extensions also for Java, C#, Fortran, . . . available Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 9/25
  • 13. Python Extending/Integrating A Real World Example Tips Summary Extending/Integration The Contestants: The “classic way” . . . Extending and Embedding the Python Interpreter The “new way” . . . Python ctypes SWIG Boost.Python Others: SIP Pythonizer SILOON (Pyrex) Extensions also for Java, C#, Fortran, . . . available Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 9/25
  • 14. Python Extending/Integrating A Real World Example Tips Summary Boost.Python Thinking Hybrid with Boost.Python Bottom up and . . . Top down possible Develop quickly Resolve bottle necks Donald Knuth’s: “Premature optimisation is the root of all evil.” or: Don’t Optimise Now! Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 10/25
  • 15. Python Extending/Integrating A Real World Example Tips Summary Boost.Python Thinking Hybrid with Boost.Python Bottom up and . . . Top down possible Develop quickly Resolve bottle necks Donald Knuth’s: “Premature optimisation is the root of all evil.” or: Don’t Optimise Now! Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 10/25
  • 16. Python Extending/Integrating A Real World Example Tips Summary Boost.Python Thinking Hybrid with Boost.Python Bottom up and . . . Top down possible Develop quickly Resolve bottle necks Donald Knuth’s: “Premature optimisation is the root of all evil.” or: Don’t Optimise Now! Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 10/25
  • 17. Python Extending/Integrating A Real World Example Tips Summary Hello World char const* greet(unsigned x) { static char const* const msgs[] = {quot;helloquot;, quot;Boost.Pythonquot;, quot;world!quot;}; if (x > 2) { throw std::range error(quot;greet: Index out of range.quot;); } return msgs[x]; } #include <boost/python.hpp> using namespace boost::python; BOOST PYTHON MODULE(hello) { .def(quot;greetquot;, greet, quot;return one of 3 parts of a greetingquot;); } And here it is in action: >>> import hello >>> for x in range (3): ... print hello . greet ( x ) ... hello Boost . Python world ! Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 11/25
  • 18. Python Extending/Integrating A Real World Example Tips Summary Boost.Python One of a few libraries that make it easy to integrate C++ and Python code How does it pull off this trick? Template meta–programming (i. e. Don’t ask!) Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 12/25
  • 19. Python Extending/Integrating A Real World Example Tips Summary Boost.Python One of a few libraries that make it easy to integrate C++ and Python code How does it pull off this trick? Template meta–programming (i. e. Don’t ask!) Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 12/25
  • 20. Python Extending/Integrating A Real World Example Tips Summary See it Happen I’m making it work for you now . . . [“MyClass” demonstration (MyClass.cpp, MyClass.h, mymodule.cpp)] Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 13/25
  • 21. Python Extending/Integrating A Real World Example Tips Summary Outline 1 Python 2 Extending/Integrating 3 A Real World Example 4 Tips Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 14/25
  • 22. Python Extending/Integrating A Real World Example Tips Summary A Real World Example Re-visiting NaSt2D Wrapping NaSt2D Control the code Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 15/25
  • 23. Python Extending/Integrating A Real World Example Tips Summary NaSt2D in Python This is what I’m going to show you: Code to be wrapped Generated wrapper code Generator script SCons (build system) How it works with Python [Wrapped NaSt2D demonstration (Wrapper.h, nast2dmodule.cpp, generate bindings.py, SConstruct, demo0.py)] Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 16/25
  • 24. Python Extending/Integrating A Real World Example Tips Summary Extend Wrapper Class Inheriting from C++ classes Interfacing numerical values Change functionality Follow the Computation Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 17/25
  • 25. Python Extending/Integrating A Real World Example Tips Summary Overriding in Python This is what I’m going to show you: Overriding a native method in Python Native method needs to be “virtual” Live data plotting with GNUplot [NaSt2D with plotting demonstration (demo1.py, demo2.py)] Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 18/25
  • 26. Python Extending/Integrating A Real World Example Tips Summary Do more Computations Parameter Study Change input file Compute several cases Plot results automatically Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 19/25
  • 27. Python Extending/Integrating A Real World Example Tips Summary Automating in Python This is what I’m going to show you: Using a template input file Batch–calculating several runs Plotting results with GNUplot [NaSt2D with parameter variation demonstration (demo3.py, demo4.py)] Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 20/25
  • 28. Python Extending/Integrating A Real World Example Tips Summary Outline 1 Python 2 Extending/Integrating 3 A Real World Example 4 Tips Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 21/25
  • 29. Python Extending/Integrating A Real World Example Tips Summary Tips To override C++ methods: make them virtual C/C++ pit fall Call by reference/value Solution: calling policies Map to “other/sane” languages Java: Jython C#: IronPython Fortran: PyFort, Py2F (Native to other: SWIG) Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 22/25
  • 30. Python Extending/Integrating A Real World Example Tips Summary Summary Why is Python good for you? How can performance bottle necks be resolved? Advantages of “Thinking Hybrid” Python–native wrapping using Boost.Python Automated wrapper generation SCons build system Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 23/25
  • 31. Python Extending/Integrating A Real World Example Tips Summary Python and the “Need for Speed” Cuong Do – Software Architect YouTube.com “Python is fast enough for our site and allows us to produce maintainable features in record times, with a minimum of developers.” Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 24/25
  • 32. Python Extending/Integrating A Real World Example Tips Summary Questions? G.Kloss@massey.ac.nz Slides and code available here: http://www.kloss-familie.de/moin/TalksPresentations Guy K. Kloss — Thinking Hybrid – Python/C++ Integration 25/25