Calling C++ function from Pyhon OS (Windows 7 also works) Windows 8.1 Compiler Visual Studio 2013 Update4 Python (Other version may be incompatible) python-3.3.5.msi (x86) [1] SWIG (Unzip and copy swigwin-3.0.2 folder to C:\) swigwin-3.0.2 [2]

1. SWIG Hello world
Calling C++ function from Pyhon
2014/12/20
Jacky Liu

2. • This slide organize instructions from “Falldog的程
式戰場 - [Python] Windows底下 使用SWIG呼叫
C/C++的function” (http://falldog7.blogspot.tw/2013/07/python-
swig-c-function.html)

3. Environment Setting
• OS (Windows 7 also works)
Windows 8.1
• Compiler
Visual Studio 2013 Update4
• Python (Other version may be incompatible)
python-3.3.5.msi (x86) [1]
• SWIG (Unzip and copy swigwin-3.0.2 folder to C:)
swigwin-3.0.2 [2]
[1] http://www.python.org/ftp/python/3.3.5/python-3.3.5.msi
[2] http://sourceforge.net/projects/swig/files/swigwin/swigwin-3.0.2/

4. SWIG Hello world
• Our goal is to call a simple C++ function from
python.
int AddOne(int n) { return n + 1; }
int Sqrt(int n) { return n*n; }
print(Sample.AddOne(1)) # >>> 2
print(Sample.Sqrt(2)) # >>> 4
C++
Python

5. New project

6. New project
Name=Sample

7. New project

8. New project
1. DLL
2. Empty project
3. Finish

9. Project setting
• Project setting - Include Python header files
> Right click >

10. Project setting
• Properties | Configuration Properties | VC++ Directories
Executable Directories: C:swigwin-3.0.2

11. Project setting
• Project | Properties | Configuration Properties | C/C++
Additional Include Directories: C:Python33include

12. Project setting
• Properties | Configuration Properties | Linker
Additional Library Directories: C:Python33libs

13. Project setting
• Properties | Configuration Properties | Build Events | Pre-Build Event
swig.exe -c++ -python -o $(ProjectDir)Sample_wrap.cxx $(ProjectDir)Sample.i

14. Add file
• Add Sample.h
#include "Python.h"
int AddOne(int n);
int Sqrt(int n);
PyObject* SqrtInPyObj(PyObject* obj);

15. Add file
• Add Sample.cpp
#include "Sample.h"
int AddOne(int n)
{
return n + 1;
}
int Sqrt(int n)
{
return n*n;
}
PyObject* SqrtInPyObj(PyObject* obj)
{
int n = PyLong_AsLong(obj);
return Py_BuildValue("i", n*n);
}

16. Add file
• Add Sample.i
%module Sample
%{
#include "Sample.h"
%}
%include "Sample.h"

17. Generate files
• Build “Release” (F7)
Generate
• $(ProjectDir)/Release/Sample.dll
• $(ProjectDir)/Sample/Sample.py
• $(ProjectDir)/Sample/Sample_wrap.cxx
• Add Sample_wrap.cxx back to project

18. Configure Linker output file name
$(OutDir)_$(ProjectName).pyd

19. Add preprocessor definitions
__WIN32__

20. Generate .pyd file for python
• Build “Release” (F7) again
Generate
• $(ProjectDir)/Release/_Sample.pyd

21. Try it in Python
• Copy
• $(ProjectDir)/Release/_Sample.pyd
• $(ProjectDir)/Sample/Sample.py
• To the same folder with your script
• Test.py
import Sample
print Sample.AddOne(1) # >>> 2
print Sample.Sqrt(2) # >>> 4
print Sample.Sqrt(3) # >>> 9
print Sample.SqrtInPyObj(2) # >>> 4
print Sample.SqrtInPyObj(3) # >>> 9

22. Reference
• Falldog的程式戰場 - [Python] Windows底下 使用
SWIG呼叫C/C++的function