Python Advanced functional Programming (function as parameter)

<title>What is functional programming?</title> What is functional programming?

Functions: function
Functional type: Functional, a programming paradigm

functional programming is a programming mode of abstract computation
function ≠ function, for example: calculate ≠ computer

In the computer, the computer hardware is the lowest level, and the higher the language the more advanced

Low--------------------------------->High
Computer Hardware-->Assembly Language-->C language-->Python language
  ↓                    ↓         ↓
 instruction                 function      function Type
Computer------------------------>calculation (mathematics)

0 features of functional programming

• Treat calculations as functions rather than directives
• Pure functional Programming: No variables required, no side effects, simple testing
• Supports higher-order functions with simple code

0 Python-supported functional programming has the following features:

• Not purely functional programming: allowed variables
• Supports higher order functions: Functions can also be passed in as variables
• Support closures: the ability to return functions with closures
• Support anonymous functions in a limited way

Take a function as a parameter

0 What is a higher order function?

• Variables can point to functions
  For example, there is a function called abs in Python (for absolute value)

>>> abs(-10)
10
>>> abs
<built-in function abs>
>>> f=abs
>>> f(-20)
20

• A function name is actually a variable that points to a function
  Same as ABS function

>>>ABS
<built-inch  function abs>
>>>ABS=Len
>>>ABS(-Ten)
Traceback (most recent call Last):
File"<stdin>", Line 1,inch<module>
Typeerror:object ofType' int 'Has noLen()
>>>ABS([1,2,3])
3

If we point the ABS variable to another function of the function, then ABS is no longer an absolute function, and this time it will be an error. This time abs points to the Len function. This time we give ABS a list, we can call the normal. There is no difference between a function name and a normal variable, which points to a function name.

• Higher order functions: functions that can receive function parameters
  
  • Variables can point to functions
  • Parameters of a function can receive variables
  • A function can receive another function as a parameter
  • Functions that can receive functions as arguments are higher-order functions.

Example: Receiving ABS function

• Define a function to receive x,y,f three parameters
• where x, Y is a number, F is a function

>>>def add(x,y,f):
...return f(x)+f(y)
...
>>> add(-5,9,abs)
14

The code above, as defined by the function, actually executes the code:

abs(-5)+abs(9)

Since the parameters x, Y and F can be arbitrarily passed in, if F is passed in to other functions you can get different return values

again for example: calculation
(The square root can be computed with a function: math.sqrt() )

import math

def add(x,y,f):
    return f(x)+f(y)

print add(25,9,math.sqrt)

Python Advanced functional Programming (function as parameter)