In Python, closures are functions that remember the values from the enclosing lexical scope even when the scope has been deleted or the function has finished executing. This means that closures can access and modify variables that are no longer in scope, as long as the closure itself is still in memory.
When a closure is created, it retains a reference to the variables in its enclosing scope. This reference prevents the variables from being garbage collected when the enclosing scope is deleted. As long as the closure exists, the variables it references will continue to exist in memory.
Here's an example:
def outer_function(x): def inner_function(y): return x + y return inner_functionclosure = outer_function(5)print(closure(3)) # prints 8del outer_functionprint(closure(3)) # prints 8 |
In this example, we define the outer_function that takes an argument x and returns the inner_function. The inner_function takes an argument y and returns the sum of x and y. We then create a closure by calling outer_function(5) and assign it to the variable closure.
Even though we delete outer_function after creating the closure, we can still call closure and it will correctly sum 5 and 3 to give 8.
This is because the closure retains a reference to the x variable from the outer_function, preventing it from being garbage collected even after the outer_function has been deleted.
In summary, closures can access and modify variables from their enclosing scope even after the scope has been deleted, as long as the closure itself is still in memory. This behavior can be useful in certain situations, but it's important to be aware of it and use it with caution to avoid memory leaks and other unexpected behavior.