Python closure functions

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  1. A closure in Python refers to a function object that remembers values in enclosing scopes even if they are not present in memory. It is a record storing a function together with an environment: a mapping associating each free variable of the function (variables that are used locally but defined in an enclosing scope) with the value or reference to which the name was bound when the closure was created.

    Closures are used to avoid the use of global values and to provide some form of data hiding. They can also provide an object-oriented solution to the problem.

    Here is how you can define and use a closure in Python:

    1. Define a Nested Function: In Python, we have functions defined inside other functions. The inner function will be the closure.

    2. The Inner Function Must Refer to a Value Defined in the Enclosing Function: The closure should refer to a variable that is non-local, i.e., not defined in the inner function but defined in the enclosing function.

    3. The Enclosing Function Must Return the Closure: The outer function must return the inner function (closure).

    Here is an example to illustrate:

    def outer_function(text):
        def inner_function():
            print(text)
        return inner_function
    
    my_closure = outer_function("Hello, World!")
    my_closure()
    

    In this example, outer_function is an enclosing function and inner_function is the closure that captures and remembers the value of the variable text defined in outer_function.

    When outer_function is called with the argument "Hello, World!", it returns the inner_function, which is then called using my_closure(). Despite outer_function has completed its execution, inner_function still has access to the variable text which was in the scope of outer_function.

    Closures are thus a powerful tool in Python, enabling the creation of function objects with some hidden state - the state being the local variables of the enclosing scope.

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