生成器特性阐释

  #生成器函数一定要next之后才是执行

人口普查：

{'name':'北京','population':10}
{'name':'山东','population':10}
{'name':'山西','population':31}
{'name':'河北','population':33}
{'name':'台湾','population':33}

def get_polulation():
    with open('人口普查', 'r', encoding='utf-8') as f:  #打开文件
        for i in f:
            yield i


g=get_polulation()
g.__next__()
g.__next__()
g.__next__()
g.__next__()
# print(g.__next__()['population'])  #错误 因为g.next得到的是字符串 不能直接索引 需要转化为字典 用eval提取字符串里面的字典 从而索引定位到人口数
# s1=eval(g.__next__())
# print(type(s1))
# print(s1['population'])
# res=0
# for p in g:
#     p_dic=eval(p)
#     print(p_dic['population'])
#     res+=p_dic['population']
# print(res)

all_pop=sum(eval(i)['population'] for i in g)   #总人数
print(all_pop)


for p in g:
    print('%s %%' %eval(p)['population']/all_pop)