What does closure mean?

What does closure mean? Specific code examples are required

Closure (Closure) is a special programming concept used to describe a function (called an internal The relationship between a function) and the variables it references (called free variables). Simply put, closure means that a function can access and operate variables outside the scope of its definition.

Before understanding closures, let’s first look at a simple code example:

def outer_func(x):
    def inner_func(y):
        return x + y
    return inner_func

add_5 = outer_func(5)
print(add_5(3))  # 输出结果为8

In the above code, outer_func is an external function, which returns an Internal function inner_func. The variable x is defined in outer_func, and this variable is used in the inner function inner_func.

When we call outer_func(5), it returns an inner_func function object and sets the value of x to 5. We assign the returned function object to add_5. Next, when add_5(3) is called, it passes argument 3 to inner_func, adds it to the value of x and returns the result.

It is worth noting here that inner_func can access and operate x outside its definition scope, even if outer_func has completed execution. This is an important feature of closures.

As can be seen from the above code examples, the characteristics of closures are:

1. Internal functions can access variables defined in external functions.
2. External function returns the internal function object.

The benefit of closures is that they allow us to create a function that saves state. In the above example, each call to add_5 will use the previously defined value of x. This ability is very useful in programming.

In addition to the above Python examples, closures also exist in other programming languages. For example, in JavaScript, closures are very common. Here is an example of a closure in JavaScript:

function outerFunc(x) {
  return function innerFunc(y) {
    return x + y;
  };
}

var add5 = outerFunc(5);
console.log(add5(3)); // 输出结果为8

The code here is very similar to the Python example, only the syntax is different. By returning the innerFunc function object in the outerFunc function, we create a closure and be able to access and manipulate x in the innerFunc.

In conclusion, closure is a powerful programming concept that provides a way to still access and operate variables outside the scope of its definition after the function has completed execution. Closures are widely used in programming, which can simplify code logic and improve code readability and maintainability.

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