# 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

```python
import weakref
```

## Creating Weak References

You can create a weak reference using `weakref.ref()`.

```python
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.

```python
print(r()) # Output: <__main__.MyClass object at ...>
r().my_method() # Output: Hello
```

If the object has been garbage collected, calling the weak reference returns `None`.

```python
del obj
print(r()) # Output: None
```

## Weak 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.

```python
d = weakref.WeakValueDictionary()
```

[[programming/python/python]]