Closure, decorator

Closure ：
characteristic ：
1. There is a function in the function
2. The inner function must use the outer function variable
3. The return value must be an inner function
Be sure to write it down

# Electronic scale
# Can calculate :
Price =（ Gross weight - Packing weight ）* The unit price
Packing weight ：0.1 Jin
Price =（ Gross weight -0.1）* The unit price
Apple ：3 element / Jin
Banana ：5 element / Jin

def price(weight,unitPrice):
	return (weight-0.1)*unitPrice
apple=price(10.1,3)
print(apple)
banana=price(10.1,5)
print(banana)

Closure

def price(unitPrice):
	def computer(weight):
        	return (weight-0.1)*unitPrice
	return computer
apple=price(3)#  Don't execute , Equivalent to return value function computer
print(apple(10.1))
banana=price(5)
print(banana(10.1))

practice ：
Construct a closure program , Be able to calculate the square as needed 、 cube .

def jisuan(x):
    def a(y):
        return y**x
    return a
pingfang=jisuan(2) #2 yes jisuan Parameter variables for 
print(pingfang(5))


def jisuan(x):
    def b(y):
        return y**x
    return b
lifang=jisuan(3)
print(lifang(9))

Decorator （ Decorators ）：
（ Have time to explain in detail ）
Design a decorator , Able to calculate the circular area 、 Square area .

import math
def jisuan(mianji):
    def kkk(*args,**kwargs):
        print("==== area ====")
        x=mianji(*args,**kwargs)
        return x
    return kkk
@jisuan
def mianji1(r):
    return math.pi*r**2
@jisuan
def mianji2(d):
    return d**2
print(mianji1(3))
print(mianji2(5))

Running results ：
area
28.274333882308138
area
25