Is it possible to 'import * from DIRECTORY', then somehow (anyhow) iterate over the loaded modules?

Let me explain the use case...

In a simple python web application framework designed for Google App Engine, I'd like to have my models loa开发者_开发问答ded automatically from a 'models' directory, so all that's needed to add a model to the application is place a file user.py (for example), which contains a class called 'User', in the 'models/' directory.

Being GAE, I can't read from the file system so I can't just read the filenames that way, but it seems to me that I must be able to 'import * from models' (or some equivalent), and retrieve at least a list of module names that were loaded, so I can subject them to further processing logic.

To be clear, I want this to be done WITHOUT having to maintain a separate list of these module names for the application to read from.

You can read from the filesystem in GAE just fine; you just can't write to the filesystem.

from models import * will only import modules listed in __all__ in models/__init__.py; there's no automatic way to import all modules in a package if they're not declared to be part of the package. You just need to read the directory (which you can do) and __import__() everything in it.

As explained in the Python tutorial, you cannot load all .py files from a directory unless you list them manually in the list named __all__ in the file __init__.py. One of the reasons why this is impossible is that it would not work well on case-insensitive file systems -- Python would not know in which case the module names should be used.

Let me start by saying that I'm not familiar with Google App Engine, but the following code demonstrates how to import all python files from a directory. In this case, I am importing files from my 'example' directory, which contains one file, 'dynamic_file.py'.

import os
import imp
import glob

def extract_module_names(python_files):
    module_names = []
    for py_file in python_files:
        module_name = (os.path.basename(py_file))[:-3]
        module_names.append(module_name)
    return module_names

def load_modules(modules, py_files):
    module_count = len(modules)
    for i in range(0, module_count):
        globals()[modules[i]] = imp.load_source(modules[i], py_files[i])

if __name__ == "__main__":
    python_files = glob.glob('example/*.py')
    module_names = extract_module_names(python_files)
    load_modules(module_names, python_files)
    dynamic_file.my_func()

Also, if you wish to iterate over these modules, you could modify the load_modules function to return a list of the loaded module objects by appending the 'imp.load_source(..)' call to a list.

Hope it helps.