def getpopulation():
    with open('a.txt',encoding='utf-8') as f:
        for i in f:
            yield i
getP = getpopulation()
getPnum = eval(getP.__next__())
print(getPnum['population'])

def getpopulation():
    with open('a.txt',encoding='utf-8') as f:
        for i in f:
            yield i
getP 
 
= getpopulation()
all_pop = sum(eval(i)['population'] for i in getP)   #獲取總人數
print(all_pop)

#注意：迭代只能迭代一次，這裡getP在上邊已經迭代過了，所以下面的for迴圈不能在使用
#可以重新賦值給兩一個變數

for i in getP:
    print('%s %%' %eval(i)['population']/all_pop)

#yield 相當於return 控制的是函式的返回值
#x=yield的另外一個特性，接收send傳過來的值賦給x

def test():
    
 
print('開始了')

    fisrt = yield 1
    print('第一次',fisrt)

    yield 2
    print('第二次')
t = test()
res = t.__next__()
print(res)
t.send(None)   #可以觸發生成器執行
res = t.send('函式停留在哪兒，我就在哪兒賦值')   #可以觸發生成器執行
print(res)