How to Implement Dynamic Attribute Access with __getattr__-like Behavior in Modules?

Implementing __getattr__-like Behavior on a Module

Problem Statement:

To extend a module with __getattr__-like functionality that dynamically creates instances of a class and invokes methods on them when accessing attributes that do not exist in the module.

Approach: Wrap the Module Functionality

While getattr methods commonly operate on classes, it is not directly applicable to modules. To address this, a wrapper function can be implemented to redirect attribute access to an instance of a substitution class.

Step 1: Implement the Substitution Class

<code class="python">class Wrapper:
    def __init__(mod):
        setattr(mod, '__getattr__', getattrmod)</code>

This wrapper class provides a customized getattr method called getattrmod.

Step 2: Replace the Module with the Wrapper

<code class="python">sys.modules[__name__] = Wrapper</code>

By replacing the module itself with the wrapper, any future attribute access on the module will be intercepted by the getattr method.

Step 3: Define getattr Method

<code class="python">def getattrmod(mod, attr):
    # Create an instance of the substitution class
    instance = Class()

    # Invoke the method with the same name as the missing attribute
    return getattr(instance, attr)</code>

Warning: Caveats and Limitations

• The wrapper will replace all attributes of the module, so any existing functions or variables will be lost.
• To support importing all module elements, the substitution class must define a all attribute.
• Be aware of potential performance implications if the substitution class is instantiated for every attribute access.

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