生成器实例

def jidan():
    for i in range(10):
        yield'鸡蛋%d' %i
#jd：生成器 自动实现迭代器协议
jd = jidan()
print(jd.__next__())
print(jd.__next__())

包子问题：

def product_bz():
    for i in range(10):
        print('正在生产包子')
        yield '包子%s'%i
        print('开始卖包子了')
bz_list = product_bz()
print(bz_list.__next__())
#加代码
print(bz_list.__next__())

运行结果：

正在生产包子
包子0
开始卖包子了
正在生产包子
包子1

　

　　人口普查：

{'city':'北京','population':23}
{'city':'西安','population':13}
{'city':'上海','population':123}
{'city':'南京','population':12}
{'city':'成都','population':12345}

　　

# #获取某一地区的人口数
def get_population():
    with open('人口普查','r',encoding='utf-8') as f:
        for i in f:
            yield i
print(get_population())
get_p = get_population()
s = (eval(get_p.__next__()))
print(type(s))
print(s['population'])
 

运行结果：

<generator object get_population at 0x02D86270>
<class 'dict'>
23

Process finished with exit code 0

　　

# #使用生成器迭代出所有城市的人口数
def get_population():
    with open('人口普查','r',encoding='utf-8') as f:
        for i in f:
            yield i
print(get_population())
get_p = get_population()
# print(get_p)
for p in get_p:
    p_dict = eval(p)
    print(p_dict['population'])

运行结果：

<generator object get_population at 0x01376270>
23
13
123
12
12345

Process finished with exit code 0

　　

# #计算总人口数
def get_population():
    with open('人口普查','r',encoding='utf-8') as f:
        for i in f:
            yield i
print(get_population())
get_p = get_population()
all_pop = sum(eval(i)['population'] for i in get_p)
print(all_pop)

运行结果：

<generator object get_population at 0x03716270>
12516

Process finished with exit code 0

　　

#计算平均人口数 失败
def get_population():
    with open('人口普查','r',encoding='utf-8') as f:
        for i in f:
            yield i
print(get_population())#生成器
get_p = get_population()
all_pop = sum(eval(i)['population'] for i in get_p)
print(all_pop)
for p in get_p:
    print(eval(p)['population']/all_pop)#使用__next__()之后所有数字被遍历完 计算平均数失败

运行结果：

<generator object get_population at 0x02F96270>
12516#计算失败

Process finished with exit code 0

　　

def test():

    for i in range(4):
        yield i
t = test()
t1 = (i for i in t)
t2 = (i for i in t1)
print(list(t1))
print(list(t2))#在这之前t1已经遍历过 此时已经遍历结束为空 打印出来空列表

运行结果：

[0, 1, 2, 3]
[]#之前被遍历过 此时为空

Process finished with exit code 0