FreeOrion

I don't know any C++, however I'd consider myself good at Python (after all I use python all day at work). Knowing part of this game is done in Python I was wondering if I could be of any help. Unfortunately I've never worked on a mixed language project and have no experience with writing Python code to be used in a C++ app. So for someone new to this kind of stuff and a total Python geek, what could I dive into?

Python 2.6 in FreeOrion is currently used only for AI scripting.

The relevant .py files are located in the /default/AI directory. To start AI programming, all you need to do is edit those files, or add new ones as appropriate.

There is some out of date documentation of the API on the wiki. Most it is still accurate, but there have been some changes since it was updated.

If you run into problems, you can always look at the C++ code that exposes the interface to Python. It might be tricky to get all the details of what various functions expect or do, but at the least you can see what functions, properties and objects are available in the general order-giving interface code and the various class exposing code files.

To start, looking over the existing Python code is probably the best way to start.

I'm having a bit difficulties when I'm trying to experiment with the Python scripts. I read somewhere that you don't have to rebuild the project if you modify the scripts. So all that has to be done is to modify, save the script and run freeorion.exe?

Yes.

It might actually be possible to modify the AI scripts while the program is running, though I haven't tried this myself.

Just make sure you're editing scripts in the right location, which is within the resource directory the progam is currently using, which is generally the default directory inside the FreeOrion directory where the executables / binaries are located. If you're got an old config.xml or have modified the resource directory, it could be somewhere else, though.

Also, if you're trying to modify files in Program Files on Vista or Win7, it might cause problems because the OS doesn't like you modifying files there. So, it's suggested to put the resource directory somewhere else / use the SDK if developing AI scripts.

I'm editing files in the ...\FreeOrion\default\AI. I'm trying to create some kind of a debug file from the scripts that I can see what's happening, but for example the code below doesn't do anything.

What is "..." in that path?

Check AI_1.log for error messages and debug output. Your attempts to open and write a file might not be successful, and the error message might tell you why.

To generate debug output, just use print "whatever you want to say" and then read it in the log file.

Ok, that's a good hint.

Which is why it's mentioned on the Python API wiki page.

But it doesn't say the name or location of the file.

Now it does.

I would like to add function immediateneighbors(...) in universe.cpp to the python API. What do I have to do? Also how do you loop through an array that has a double as an index?

If you want to return a std::map<double, int> to Python, you'll need to use the map_indexing_suite to expose that class to Python, similar to how the vector_indexing_suite is used in PythonAI.cpp (section titled in comments: STL Containers) to expose the vectors of int and std::string. Then you should be able to add the function to the Universe class in PythonUniverseWrapper.cpp using .def, similar to:
I don't know whether you'd need to do anything with return value policies for this function, but if you did, return by value would seem appropriate.


It's a map, not an array. You can use
to iterate through it in C++. In Python, I'm not sure exactly how the resulting data structure would appear and function, but presumably it would be similar to a Python dict.