Import folder of modules in Python

Question

Is it possible in python to get a list of modules from a folder/package and import them?

I would like to be able to do this from a function inside a class, so that the entire class has access to them (possibly done from the __init__ method).

Any help would be greatly appreciated.

• Hannele: Are from package import * and dir(package) insufficient? Note that dir is a Python command, as well as a command line one.
• Eric Wilson: @Hannele Does that really work for you? I get ['__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__'] without any mention of the modules in package. dir shows the modules if the modules themselves are explicitly imported, though, but that defeats the purpose of the question.
• Hannele: I might have to double-check how that works with a folder - do you have an __init__.py file in the folder? Even empty, this is what tells python to treat the folder as a module.
• Eric Wilson: Yes, I had an __init__.py. What I didn't have is what @MarkHildreth helpfully referenced: the line __all__ = ['bar','baz'] in __init__.py.

Answer 1

See the modules document.

The only solution is for the package author to provide an explicit index of the package. The import statement uses the following convention: if a package’s __init__.py code defines a list named __all__, it is taken to be the list of module names that should be imported when from package import * is encountered. It is up to the package author to keep this list up-to-date when a new version of the package is released. Package authors may also decide not to support it, if they don’t see a use for importing * from their package. For example, the file sounds/effects/__init__.py could contain the following code:

__all__ = ["echo", "surround", "reverse"]

This would mean that from sound.effects import * would import the three named submodules of the sound package.

Yes, you could find a way to do this by doing a directory listing for the files in the directory and import them manually. But there isn't built-in syntax for what you're asking.

Answer 2

You can know the list of the modules with the dir function

import module
dir (module)

Later in a program, you can import a single function :

from module import function

• Eric Wilson: When I try dir(foo) (with foo being a package) I get ['__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__'] which doesn't contain a list of the modules in the package.
• Griffin: @EricWilson >>> type(dir(sys)) <type 'list'>
• Mark Hildreth: This won't get you the list of modules. This will get you the list of attributes for the package (as defined in the __init__.py file of the package's directory). The modules for the package are only included in this list if they are explicitly stated in the __all__ variable.

Answer 3

The distribute module provides a mechanism that does much of this. First, you might start by listing the python files in a package using pkg_resources.resource_listdir:

>>> module_names = set(os.path.splitext(r)[0] 
... for r
... in pkg_resources.resource_listdir("sqlalchemy", "/")
... if os.path.splitext(r)[1] in ('.py', '.pyc', '.pyo', '')
... ) - set(('__init__',))
>>> module_names
set(['engine', 'util', 'exc', 'pool', 'processors', 'interfaces', 
'databases', 'ext', 'topological', 'queue', 'test', 'connectors',
'orm', 'log', 'dialects', 'sql', 'types', 'schema'])

You could then import each module in a loop:

modules = {}
for module in module_names:
 modules[module] = __import__('.'.join('sqlalchemy', module))