协程
- 迭代器
- 可迭代(Iterable): 直接作用于For循环的变量”,
- 迭代器():不但可以作用于for循环,还可以被next调用”,
- list是一个典型的可以迭代对象,但不是迭代器”,
- 通过isinstance判断”,
- iterable 和 iterator可以转换”,
- 通过 iter函数可以进行转换”
l = [i for i in range(10)]
for idx in l:
print(idx)
for i in range(2):
print(i)
from collections import Iterable
ll = [1,2,3,4,5]
print(isinstance(ll,Iterable))
from collections import Iterator
print(isinstance(ll,Iterator))
True
False
s = "I love You"
print(isinstance(s,Iterable))
print(isinstance(s,Iterator))
s_iter = iter(s)
print(isinstance(s_iter,Iterable))
print(isinstance(s_iter,Iterator))
True
False
True
True
生成器,
- generator : 一边循环一边计算下一个元素的机制/算法
- 需要满足三个条件
- 每次调用都生产出for 循环需要的下一个元素
- 如果达到最后一个后,爆出StopIteration异常
- 可以被next函数调用
- 如何生成一个生成器
- 直接使用
- 如果函数中包含yield,则这个函数就叫做生成器
- next 调用函数,遇到yield返回
L = [x*x for x in range(5)]
g = (x*x for x in range(5))
print(type(L))
print(type(g))
<class 'list'>
<class 'generator'>
def odd():
print("Step 1")
yield 1
print("Step 2")
yield 2
print("Step 3")
yield 3
g = odd()
one = next(g)
print(one)
two = next(g)
print(two)
three = next(g)
print(three)
Step 1
1
Step 2
2
Step 3
3
def fib(max):
n,a,b = 0,0,1
while n < max:
yield b
a,b = b, a+b
n += 1
return 'Done'
g = fib(5)
for i in range(6):
rst = next(g)
print(rst)
1
1
2
3
5
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
<ipython-input-14-526d3727af54> in <module>()
11
12 for i in range(6):
---> 13 rst = next(g)
14 print(rst)
StopIteration: Done
ge = fib(10)
""",
生成器的典型用法是在for 循环中使用,
比较常用的典型生成器就是range,
"""
for i in ge:
print(i)
1
1
2
3
5
8
13
21
34
55
协程,
- 历史历程,
- 3.4 引入协程,用yield实现,
- 3.5 引入协程语法,
- 实现的协程比较好的包有asyncio, tornado,gevent,
- 定义:协程 是为非抢占式多任务产生子程序的计算机程序组件,协程允许不同入口点在不同位置暂停或开始执行程序。,
- 从技术角度讲,协程就是一个你可以暂停执行的函数,或者干脆把协程理解成一个协程的生成器,
- 协程的实现,
- 协程的四个状态,
- inspect.getgeneratorstate(…) 函数确认,该函数会返回下述字符串的一个:,
- GEN_CREATED:等待开始执行,
- GEN_RUNNING:解释器正在执行,
- GEN_SUSPENED:在yield表达式处暂停,
- GEN_CLOSED:执行结束,
- next预计(prime),
- 协程终止,
- 协程中未处理的异常会向上冒泡,传给next函数或者send函数的调用方,
- 终止协议的一个方式:发送某个哨符值,让协程退出,内置的None 和Ellipsis等常量经常作用哨符值。,
- yield from,
- 调用协程为了得到返回值,协程必须正常终止,
- 生成器正常终止会发出StopIteration异常,异常对象的value属性保存返回值,
- yield form从内部捕获StopIteration异常”
- 委派生成器
- 包含yield from 表达式的生成器函数
- 委派生成器在yield from表达式处暂停,调用方可以直接把数据发给子生成器
- 子生成器在把产生的值发给调用方
- 子生成器在最后,解释器会抛出StopIteration,并且把返回值附加到异常对象上。
def simple_coroutine():
print("-> start")
x = yield
print("-> recived",x)
sc = simple_coroutine()
print(111)
next(sc)
print(222)
sc.send("Zhexiao")
111
-> start
222
-> recived Zhexiao
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
<ipython-input-17-e71ccdf74e36> in <module>()
11 next(sc) # 预计
12 print(222)
---> 13 sc.send("Zhexiao")# 主进程给协程发一个信号"
StopIteration:
def simple_coroutine(a):
print("-> start")
b = yield a
print("-> recived",a,b)
c = yield a + b
print("-> recived",a,b,c)
sc = simple_coroutine(5)
aa = next(sc)
print(aa)
bb = sc.send(6)
print(bb)
cc = sc.send(7)
print(cc)
-> start
5
-> recived 5 6
11
-> recived 5 6 7
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
<ipython-input-19-1b59ef0da63b> in <module>()
18 bb = sc.send(6)
19 print(bb)
---> 20 cc = sc.send(7)
21 print(cc)
StopIteration:
def gen():
for c in "AB":
yield c
print(list(gen()))
def gen_new():
yield from "AB"
print(list(gen_new()))
['A', 'B']
['A', 'B']
from collections import namedtuple
"""
解释:
1、外出for 循环每次迭代会新建立一个grouper 实例,赋值coroutine变量;
2、激活协程
3、内层for循环变量字典value值,并将该value发送给协程,进行平均值计算;
4、发送哨兵,终止协程,打印计算结果
"""
ResClass = namedtuple("Res","count average")
def averager():
total = 0.0
count = 0
average = None
while True:
term = yield
if term is None:
break
total += term
count += 1
average = total / count
return ResClass(count, average)
def grouper(storages, key):
while True:
storages[key] = yield from averager()
def clinet():
process_data = {
'boys_1' : [20,18,12,32,333,43,432],
'boys_2' : [123,321,32123,3223,423,4232,23]
}
storages = {}
for k,v in process_data.items():
coroutine = grouper(storages,k)
next(coroutine)
for dt in v:
coroutine.send(dt)
coroutine.send(None)
print(storages)
clinet()
{'boys_1': Resa(count=7, averages=127.14285714285714), 'boys_2': Resa(count=7, averages=5781.142857142857)}