生成器

#列表生成式
m = [x for x in range(10)]  #[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print(m)

def add(n):
    return n*2

s = [add(x) for x in range(10)]
print(s) #[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

#方式一：
s = (x for x in range(100))
#生成器取值下面两种方式等价
# m = s.__next__()
print(next(s)) # 0
print(next(s)) # 1
#也可以用for循环
for i in s: #生成器就是可以可迭代对象
    print(i)

#方式二：yield
def foo():
    yield 1

print(foo()) #<generator object foo at 0x000001A11A30FF10> 生成器对象
for i in foo():
    print(i) #打印出一个1

def fib(max):
    n,before,after = 0,0,1
    while n < max:
        yield before
        before,after = after,after+before
        n = n + 1


print(fib(8)) #<generator object fib at 0x000001DC7CF54888>

m = fib(8)
for i in m:
    print(i)
#打印结果
#0
#1
#1
#2
#3
#5
#8
#13