Python high-order functions

What is a higher order function? Follow the example step by step

Variables can point to functions

Using Python's built-in absolute value function abs, for example, there are several ways to call

>>> ABS (-10) 10

But what if I just write abs?

>>> abs<built-in function abs>

ABS (-10) is a function call, ABS is the function itself

We know that the result can be assigned to a variable, is the function possible?

>>> x=abs ( -10) >>> x10

y=abs>>> y<built-in function abs>

Conclusion: A function can also be assigned to a variable, that is, a variable can point to a function

Use this variable to call the function and give it a try.

>>> y (-10) 10

It worked!!! ABS (-10) and Y (-10) a hair

The function name is also a variable

The ABS () function can be thought of as ABS, which points to a function that can find an absolute value.

>>> ABS = 10>>> ABS ( -10) Traceback (most recent):  File "<stdin>", line 1, in <modu Le>typeerror: ' int ' object is not callable

ABS this variable points to 10, and then call ABS (-10) will be error, indicating that ABS is really a variable, if you want to use ABS normal function, can only restart the Python interactive environment.

What is a high-order function?

Since a variable can point to a function and a function can receive a variable, is it possible to pass the function as a variable into another function?

>>> def add (x, Y, F): Return F (x) + f (Y) >>> Add ( -2, 3, ABS) 5

　　

Passing functions as arguments, such functions are called higher-order functions.

Python high-order functions