生成器

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生成器generator创建
1.由列表生成式改写
2.函数定义中有yield
生成器的调用方式
1.通过for调用
2.通过try except调用，并且获得返回值
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# l = [x*x for x in range(10)] ##[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
# g = (x*x for x in range(10)) ##<generator object <genexpr> at 0x000001ABA974ED00>
# print(l)
# print(g)

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

##for调用生成器
for n in fib(10):
    print(n)
##try except调用生成器（可提取返回值：Generator return value: done）
g = fib(10)
while True:
    try:
        x = next(g)
        print(‘g:‘,x)
    except StopIteration as e:
        print(‘Generator return value:‘,e.value)
        break

##杨辉三角生成器
def triangles(max):
    n = 0
    line = [1]
    while n<max:
        yield line
        line = [1]+[line[i]+line[i+1] for i in range(len(line)-1)]+[1]
        n+=1
    return ‘杨辉三角运行完毕‘
for item in triangles(10):
    print(item)