Scan a directory to load Python plugin from C++ - c++

Question

I want to make a C++ application that can handle both C++ and Python plugin. For the C++ part i'm fine, but I have questions about Python plugins.
What I want to do, is to have a directory with all my python plugins, and the application will load all plugins located in this directory (like Sublime Text 2).
My problem is that I don't know how to "parse" a python script to get the name of every class that inherits from my plugin interface in order to create them.
Is there a way in boost.python to do that ? (I haven't found informations about it)
Does python have module variable I can use to do this ? (I'm not so
good with python)
Do I need to use a lexer like antlr ? ( seems heavy ...)
Do I need to have a "create" function like in C++ ? (Sublime Text
2 don't seems to need that)
Finally, do you know C++ application that handle Python plugin where I can check the code ?
Thanks ;)

Answer 1

This question is a bit loaded/unclear, but I'll give it a shot.
My problem is that I don't know how to "parse" a python script to get the name of every class that inherits from my plugin interface in order to create them.
This can be done somewhat easily with a python script; perhaps you can write one and call it from your C++ application. Here is a snippet of code that finds python scripts '*.py', imports them, and looks for classes that subclass a class called PluginInterface... not sure what you need to do after that, so I put a TODO there.
def find_plugins(directory):
for dirname, _, filenames in os.walk(directory): # recursively search 'directory'
for filename in filenames:
# Look for files that end in '.py'
if (filename.endswith(".py")):
# Assume the filename is a python module, and attempt to find and load it
### need to chop off the ".py" to get the module_name
module_name = filename[:-3]
# Attempt to find and load the module
try:
module_info = imp.find_module(module_name, [dirname])
module = imp.load_module(module_name, *module_info)
# The module loaded successfully, now look through all
# the declarations for an item whose name that matches the module name
## First, define a predicate to filter for classes from the module
## that subclass PluginInterface
predicate = lambda obj: inspect.isclass(obj) and \
obj.__module__ == module_name and \
issubclass(obj, PluginInterface)
for _, declaration in inspect.getmembers(module, predicate):
# Each 'declaration' is a class defined in the module that inherits
# from 'PluginInterface'; you can instantiate an object of that class
# and return it, print the name of the class, etc.
# TODO: fill this in
pass
except:
# If anything goes wrong loading the module, skip it quietly
pass
Perhaps this is enough to get you started, although it's not really complete, and you'll probably want to understand all the python libraries being used here so you can maintain this in the future.