What is a python return function? (Instance parsing)

In the following article, let's look at what is a return function in Python. Learn about the Python return function, well, don't talk about it. Let's go into the following article.

The Python function as the return value:

Higher-order functions can also return a function as a result value, in addition to the ability to accept functions as parameters.

Let's implement the summation of a mutable parameter. In general, the function of summing is defined like this:

def calc_sum (*args):    ax = 0 for    n in args: Ax        = ax + n    return ax

But what if you don't need to sum it right away, but in the later code, and then calculate it as needed? Instead of returning the result of a sum, you can return a function that sums:

def lazy_sum (*args):    def sum ():        ax = 0 for        n in args:            ax = ax + n        return ax    return sum

When we call Lazy_sum (), we return the SUM function instead of summing the result:

>>> f = lazy_sum (1, 3, 5, 7, 9) >>> f<function lazy_sum.<locals>.sum at 0x101c6ed90>

The result of summing is actually computed when the function f is called:

>>> F () 25

In this example, we define the function sum in the function lazy_sum, and the inner function sum can refer to the arguments and local variables of the external function lazy_sum, and when Lazy_sum returns the function sum, the relevant parameters and variables are stored in the returned function, which is called " The program structure of the closure (Closure) has great power.

Note again that when we call Lazy_sum (), each call returns a new function, even if the same parameter is passed in:

>>> f1 = lazy_sum (1, 3, 5, 7, 9) >>> F2 = lazy_sum (1, 3, 5, 7, 9) >>> F1==f2false

The invocation results of F1 () and F2 () do not affect each other.