闭包的定义：一个函数内部再定义一个函数，并且这个函数用到了外部的变量，这个函数以及外部用到的变量就称为闭包。
1.用函数处理y=k*x + b
def func(k=1, b=2, x);
ret = k * x + b
print(ret)
y1 = func(0)
y2 = func(1)
y3 = func(2)2. 用类方法处理y=k*x + b
# 定义类
class Func(object):
def __init__(self, k, b):
self.k = k
self.b = b
def __call__(self, x):
ret = self.k * x + self.b
return ret
# 实例对象
y = Func(1, 2)
y1 = y(0)
y2 = y(1)
y3 = y(2)3.用闭包处理y=k*x + b
def func(k, b);
def func_x(x):
ret = k * x + b
return ret
return func_x
y = func(1, 2)
y1 = y(0)
y2 = y(1)
y3 = y(2)4.变量的作用域规则
b = 6
def pro1(a):
print(a)
print(b)
# 执行结果
1
6
b = 6
def pro1(a):
print(a)
print(b)
b = 9
# 执行结果
1
File " line 70, in <module>
p = pro1(1)
File " line 37, in pro1
print(b)
UnboundLocalError: local variable 'b' referenced before assignment
# 报错的原因是：此时函数体内的b变成了局部变量，而在print(b)时，没有找到变量b,所以会出错
# 做如下修改
b = 6
def pro1(a):
global b # 声明b是全局变量
print(a)
print(b)
b = 9
print(b)
# 执行代码结果
1
6
9
5.再议闭包
def pro3():
lst = [] # 可变类型
def pro(a):
lst.append(a)
return lst
return pro
if __name__ == '__main__':
p = pro3()
print(p(1))
print(p(2))
print(p(3))# 执行结果
[1]
[1, 2]
[1, 2, 3]
def pro5():
count = 0 # 不可变类型
sum1 = 0
def pro():
count += 1
sum1 += 1
return count, sum1
return pro
if __name__ == '__main__':
p = pro5()
print(p())
# 执行代码结果
Traceback (most recent call last):
File "bibao.py", line 72, in <module>
print(p())
File "bibao.py", line 64, in pro
count += 1
UnboundLocalError: local variable 'count' referenced before assignment
# 报错原因：此时的count是pro函数的局部变量，count = count + 1, 在函数体中没有找到count,所以会报错
# 做如下修改
def pro5():
count = 0
sum1 = 0
def pro():
nonlocal count,sum1 # 声明是自由变量，即本地作用域中的变量，即是pro5函数体中的count=0这个变量
count += 1
sum1 += 1
return count, sum1
return proif __name__ == '__main__':
p = pro5()
print(p())
# 执行结果
(1, 1)
