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Embedded Python and Packages

Started by PAndersson Apr 12, 2010 at 3:30 PM 3 replies 1.5k views

Original Post

Apr 12, 2010 at 3:30 PM

Hey all, I'm working on a game and while the game engine is written in C I have planned to write most of the gameplay functionality in python. It works well, except that I'm a bit unsure on how to make python find any python packages I have written. I have no problem making it find the C extension it needs in order to interact with the game engine though. I have looked into several solutions such as PySys_SetPath() and Py_SetProgramName() but none of them seems to help in solving this problem. Py_SetProgramName() seems to be the function that is meant for this and I call it before intializing python, with the directory where the package can be found (and yes, I define the package with a __init__.py file) relative to the games path. Py_GetPath()'s return value seems to not be affected at all no matter what path I feed Py_SetPrgoramName(). Any help in explaining how to solve this would be much appreciated!

ninmonkeys

Apr 13, 2010 at 8:19 PM

First, test with the python file in the same directory as your main exe.
Or is this working, that modules aren't?

Not totally sure on howto with C++ on top of it.
*But* if you're using python, and you have

the following file at:

c:/python/pandas/pandsLib/__init__.py

and system environment variable:
PYTHONPATH = "c:/python/pandas"

then any python file can now do:

import pandsLib# ...

AndrewBC

Apr 13, 2010 at 10:53 PM

I don't know much of anything about python's C API, but I can show you how to do it from python easily enough, and I think that will help you out. You don't -have- to set environment variables, and if it's embedded then that may not be an option anyway.

import sysimport osmodule_dir = os.path.join('C:', 'path', 'to', 'module', 'directory')sys.path.append(module_dir)import module

Now provided that module is a module that lives in C:\path\to\module\directory, you should be good to go. You can even do some crazy stuff with dynamic imports using __import__, but that's only if you only know the module name at runtime.

PAndersson

Apr 14, 2010 at 10:05 AM

Quote:
Original post by AndrewBC
I don't know much of anything about python's C API, but I can show you how to do it from python easily enough, and I think that will help you out. You don't -have- to set environment variables, and if it's embedded then that may not be an option anyway.

*** Source Snippet Removed ***

Now provided that module is a module that lives in C:\path\to\module\directory, you should be good to go. You can even do some crazy stuff with dynamic imports using __import__, but that's only if you only know the module name at runtime.

Thanks a lot, it seem to work well when I add the variable to sys.path. Though unsure if running a bit of python code in the C funtion that initialzes the C engine actually is a good way to do it.

PAndersson

Apr 14, 2010 at 4:19 PM

Incase anyone wonders, I got it to work exactly as I want it too. Apparently the sys.path variable can look for paths relative to your application...
Here is the source C code used, works like a charm

	char pacPath[124]; //Path to python packages and modules	char modPath[5120]; //Module path	//Define path to script folder	strcpy(pacPath, "Data\\Scripts");	//Append module path to list of all python module paths	strcpy(modPath, Py_GetPath());	strcat(modPath, ";");	strcat(modPath, pacPath);	Py_Initialize();	//Update module path	PySys_SetPath(modPath);

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