生成器特性闡釋

  #生成器函數必定要next以後纔是執行

人口普查：

{'name':'北京','population':10}
{'name':'山東','population':10}
{'name':'山西','population':31}
{'name':'河北','population':33}
{'name':'臺灣','population':33}

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


g=get_polulation()
g.__next__()
g.__next__()
g.__next__()
g.__next__()
# print(g.__next__()['population'])  #錯誤 由於g.next獲得的是字符串 不能直接索引 須要轉化爲字典 用eval提取字符串裏面的字典 從而索引定位到人口數
# 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)   #總人數 print(all_pop)


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