Python Weakref Module
The weakref module allows the Python programmer to create weak references to objects. A weak reference to an object is not enough to keep the object alive: if the only remaining references to a referent are weak references, garbage collection is free to destroy the referent and reuse its memory for something else.
Importing the Module
import weakrefCreating Weak References
You can create a weak reference using weakref.ref().
import weakref
class MyClass:
def my_method(self):
print("Hello")
obj = MyClass()
r = weakref.ref(obj)
print(r) # Output: <weakref at ...; to 'MyClass' at ...>Accessing the Object
To access the original object, you call the weak reference object.
print(r()) # Output: <__main__.MyClass object at ...>
r().my_method() # Output: HelloIf the object has been garbage collected, calling the weak reference returns None.
del obj
print(r()) # Output: NoneWeak Dictionaries
The module also provides WeakValueDictionary and WeakKeyDictionary.
WeakValueDictionary
A mapping class that references values weakly. Entries in the dictionary will be discarded when no strong reference to the value exists any more.
d = weakref.WeakValueDictionary()