weakRef

weakref is a Python module that provides functionality for weak references. A weak reference is an object that does not prevent the Python garbage collector from reclaiming the object it refers to. If the object a weak reference points to is the only reference to it, the garbage collector will free the memory occupied by that object, and the weak reference will become "dead" and evaluate to None. This is distinct from a normal or "strong" reference, which keeps the object alive as long as the reference exists.

The primary use case for weak references is to create caches or mappings where you want to associate data with an object but do not want that association to prevent the object from being garbage collected if it's no longer needed elsewhere. For example, a cache could store computed results for objects. If the objects themselves are discarded, the cache entries pointing to them will automatically become invalid, preventing memory leaks.

The weakref module provides several functions and classes to work with weak references. The most common is the weakref.ref() function, which creates a weak reference to an object. Another useful class is weakref.WeakValueDictionary, which acts like a dictionary but its values are held by weak references. When the referenced object is garbage collected, the corresponding entry is automatically removed from the dictionary. Similarly, weakref.WeakKeyDictionary uses weak references for its keys. Using weak references requires careful consideration of object lifetimes and potential for references to become None unexpectedly.