Python Metaprogramming: Dynamic Module Creation

Python has great metaprogramming capabilities.

Python modules are implicitly created with a file.  It is one of the primary namespacing mechanisms in Python.  Occasionally you may wan to dynamically create one.

There are a few use cases for dynamic module creation.  The use case that comes up most frequently is modules created in the service of automated tests.  Sometimes a module is needed as input and sometimes it's needed as a mock.  Other use cases exist, but are more rare in my experience.  One I have done recently is automatic module creation to create the appropriate modules a framework or library expects. There have been other instances as well, although infrequent.  Regardless, it's a useful tool to have in your toolbox should the need ever arise.

from types import ModuleType
import sys

def make_module(new_module, doc="", scope=locals()):
    """
    make_module('a.b.c.d', doc="", scope=locals()]) -> 

    * creates module (and submodules as needed)
    * adds module (and submodules) to sys.modules
    * correctly nests submodules as needed
    """
    module_name = []
    for name in new_module.split('.'):
        m = ModuleType(name, doc)
        parent_module_name = '.'.join(module_name)
        if parent_module_name:
            setattr(sys.modules[parent_module_name], name, m)
        else:
            scope[name] = m
        module_name.append(name)
        sys.modules['.'.join(module_name)] = m
    return sys.modules['.'.join(module_name)]

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