生成器

g = (x * x for x in range(10))
print(next(g)) #0
print(next(g)) #1
print(next(g)) #4
print(next(g)) #9
print(next(g)) #16

for n in g:
    print(n) # 25 36 49 64 81

def fib(max):
    n, a, b = 0, 0, 1 # n=0 a=0 b=1
    while n < max:
        #print(b)
        yield b
        a, b = b, a + b #a=b b=a+b
        n = n + 1
    #return ‘done‘ 不能有return

f = fib(6)
print(next(f)) #1
print(next(f)) #1
print(next(f)) #2
print(‘----‘) 
for n in f: #3 5 8
    print(n)

def odd():
    print(‘step 1‘)
    yield 1
    print(‘step 2‘)
    yield 2
    print(‘step 3‘)
    yield(3)

o = odd()
print(next(o)) #1
print(next(o)) #2
print(next(o)) #3
print(next(o)) #StopIteration
#while True:
#    try:
#        x = next(o)
#        print(‘g‘, x)
#    except StopIteration as e:
#        print(‘Generator return value‘, e.value)
#        break