2018/11/16（python(迭代器与生成器)）

x=‘helloworld‘
x_t=x.__iter__()    #遵循迭代器协议，生成可迭代对象
print(x_t.__next__())
print(x_t.__next__())
print(x_t.__next__())

#for循环实质
for i in x:
    print(i)

def test():
    yield 1
    yield 2
    yield 3
g=test()
print(g)
print(g.__next__())
print(g.__next__())

# encoding:utf-8
l=[‘课程%s‘%i for i in range(10)]        #列表解析你，缺点太占用内存
print(l)

#生成器表达式
n=(‘课程%s‘%i for i in range(10))       #将列表解析[]改为（）
print(n)
print(n.__next__())
print(n.__next__())
print(n.__next__())

name=‘alex‘
result=‘woman‘ if name==‘alex‘ else ‘man‘
print(result)

m=[‘课程%s‘%i for i in range(10) if i>5]      #三元多项式
print(m)

def T():
    for i in range(100):
        print(‘第%s轮‘%i)
        yield i
        print(‘第%s轮结束‘%i)
t=T()
x=t.__next__()
print(x)
#好处中间可以加代码
t.__next__()

人口文档内容
{‘province‘:‘北京‘,‘population‘:2000000}
{‘province‘:‘天津‘,‘population‘:1000000}
{‘province‘:‘南京‘,‘population‘:3000000}
{‘province‘:‘山东‘,‘population‘:1000000}
{‘province‘:‘山西‘,‘population‘:2000000}




#代码
def fun():
    with open(‘人口‘,‘r‘,encoding=‘gbk‘) as f:
        for i in f:
            p=eval(i)
            yield p[‘population‘]
def fun2():
    s=0
    with open(‘人口‘,‘r‘,encoding=‘gbk‘) as f:
        for i in f:
            p=eval(i)
            s+=p[‘population‘]
    return s
data=fun()
s=fun2()
data_1=data.__next__()
print(data_1/s)
data_2=data.__next__()
print(data_2/s)
data_3=data.__next__()
print(data_3/s)
data_4=data.__next__()
print(data_4/s)
data_5=data.__next__()
print(data_1/s)

import time
def consum(name):
    print(‘我是%s,我开始吃包子了‘%name)
    while True:
        baozi=yield 1
        time.sleep(1)
        print(‘%s很开心的把%s吃了‘%(name,baozi))
def product():
    c1=consum(‘wupeiqi‘)
    c2=consum(‘bob‘)
    c1.__next__()
    c2.__next__()
    for i in range(5):
        time.sleep(1)
        c1.send(‘包子%s‘%i)       #把包子x传给baozi，必须传一个参数
        c2.send(‘包子%s‘%i)
product()