生成器实例-优快云博客

本文链接：https://blog.youkuaiyun.com/g_l_xz/article/details/88405953

本文通过几个具体的例子介绍了Python中生成器的使用方法，包括生成器的基本操作、利用生成器进行文件读取及数据处理等，并展示了如何计算人口普查数据中的总人口数。

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生成器实例

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

包子问题：

1 def product_bz():
2     for i in range(10):
3         print('正在生产包子')
4         yield '包子%s'%i
5         print('开始卖包子了')
6 bz_list = product_bz()
7 print(bz_list.__next__())
8 #加代码
9 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}

 1 # #获取某一地区的人口数
 2 def get_population():
 3     with open('人口普查','r',encoding='utf-8') as f:
 4         for i in f:
 5             yield i
 6 print(get_population())
 7 get_p = get_population()
 8 s = (eval(get_p.__next__()))
 9 print(type(s))
10 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

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

运行结果：

<generator object get_population at 0x03716270>
12516

Process finished with exit code 0

 1 #计算平均人口数 失败
 2 def get_population():
 3     with open('人口普查','r',encoding='utf-8') as f:
 4         for i in f:
 5             yield i
 6 print(get_population())#生成器
 7 get_p = get_population()
 8 all_pop = sum(eval(i)['population'] for i in get_p)
 9 print(all_pop)
10 for p in get_p:
11     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
#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

posted @ 2018-06-09 21:03 容颜-gl 阅读(...) 评论(...) 编辑收藏