python闭包初探

demo1:

def func():
    a = 1
    b = 2
    return a+b

def sum(a):
    def add(b):
        return a+b

    return add


num1 = func()
num2 = sum(2)

print(type(num1))
print(type(num2))
print(num2(8))

demo2:

def counter():
    cnt = [0]
    def add_one():
        cnt[0] += 1
        return cnt[0]

    return add_one

num1 = counter()
print(num1())
print(num1())
print(num1())
print("\n")

def counter(FIRST=5):
    cnt = [FIRST]
    def add_one():
        cnt[0] += 1
        return cnt[0]

    return add_one


num5 = counter(5)
print(num5())
print(num5())

闭包的使用

#计算一次函数 y = a*x + b
#不用闭包的写法
def a_line(a,b,x):
    return a*x + b


#采用 lambda 的写法
def a_line(a,b):
    return lambda x: a*x + b


line1=a_line(3,5)
print(line1(10))

#用闭包的写法
def a_line(a,b):
    def arg_y(x):
        return a*x + b
    return arg_y

line1 = a_line(3,5)
print(line1(10))