Hi all, I'm trying to create a setup which allows a program to request an object using strings and get an object of that type. It appears to be mostly working but i have difficulties if i attempt to load a module at runtime and then request an object of that type.
Essentially, my code works as follows: I have a registry class which has a method to register a class. It inserts an entry into a dictionary using a tuple of two strings (read from attributes of the class) that points to the class. It also has a method which will create an object of that class type which takes two strings as an argument. Every class i want to use this technique inherits from a class which uses a custom metaclass. The custom metaclass' __init__ function registers them with the registry class. The registry class has another method which allows you to specify a path to place your plugins in. In reality it merely appends this string to sys.path. The registry "create" function has a little extra smarts in that if it can't find the class already in the dictionary, it will attempt to load the appropriate module. It does this by using __import__ and uses the two strings supplied with a dot in between as the module name. If i manually import a module, this method works a treat, however if i attempt to dynamically load a module at runtime the create method fails with the following error: TypeError: 'NoneType' object is not callable I can see that the module is getting imported as i have set print statements in the custom metaclass to let me know when it is registering a new class. I can only conclude then that there is some difference between using the import statement and the __import__ function. I don't want to clutter the mailing list so i haven't attached any code, but i certainly can supply it assuming the answer isn't something obvious i've missed. Am i going about this completely the wrong way? Is there already an established approach for an auto-registering, dynamically loading plugin setup? Any help greatly appreciated. I'm not subscribed to the list, so please cc me in any replies. Thanks, John Allman -- http://mail.python.org/mailman/listinfo/python-list
