"""
# 16.2 用過協程的生成器的基本行為
#例子16-1 可能是協程最簡單的使用演示
def simple_coroutine():
    print(‘-> coroiutine started‘)
    x = yield
    print(‘-> coroutine recived:‘,x)
my_coro = simple_coroutine()
print(my_coro)    #<generator object simple_coroutine at 0x10900f9e8>
#print(next(my_coro))
‘‘‘
-> coroiutine started
None
‘‘‘
#my_coro.send(42)
‘‘‘
-> coroutine recived: 42
StopIteration

‘‘‘
#【備註】協程可以身處四個狀態中的一個。當前狀態可以使用inspect.getgeneratorstate()函數確定，該函數會返回下述字符串中的一個。
#... ‘GEN_CREATED‘等待開始執行。  ‘GEN_RUNNING‘ 解釋器正在執行  ‘GEN_SUSPENDED‘在yield表達式處暫停  ‘GEN_CLOSED‘執行結束。
#...因為send方法的參數會稱為暫停的yield表達式的值，所以，僅當協程處於暫停狀態時才能調用send方法。不過，如果協程還沒激活（即，狀態是‘GEN_CREATED‘），情況就不同了。因此，始終要調用next()激活協程-也可以調用my_coro.sen(None)，效果一樣
#...如果創建協程對象後立即把None之外的值發給他，會出現下述錯誤：
my_coro = simple_coroutine()
my_coro.send(1729)  #TypeError: can‘t send non-None value to a just-started generator

# 例子16-2 產出兩個值的協程
def simple_coro2(a):
    print(‘-> Started:a = ‘,a)
    b = yield a
    print(‘-> Received:b = ‘,b)
    c = yield (a+b)
    print(‘-> Received:c = ‘,c)
my_coro2 = simple_coro2(14)
from inspect import getgeneratorstate
print(getgeneratorstate(my_coro2))  #GEN_CREATED
print(next(my_coro2))
‘‘‘
-> Started:a =  14
14

‘‘‘
print(getgeneratorstate(my_coro2))  #GEN_SUSPENDED
print(my_coro2.send(28))
‘‘‘
-> Started:b =  28
42
‘‘‘
print(my_coro2.send(99))
‘‘‘
-> Received:c =  99
Traceback (most recent call last):
  File "/Users/suren/PycharmProjects/fluentPython/kongzhiliucheng/xiecheng.py", line 47, in <module>
    my_coro2.send(99)
StopIteration
‘‘‘
print(getgeneratorstate(my_coro2)) #‘GEN_CLOSED‘


#例子16-3 一個計算移動平均值的協程
def averager():
    total = 0.0
    count = 0
    average = None
    while True:#這個無限循環表明，只要調用方不斷把值發給這個協程，它就會一直接收值，然後生成結果。僅當調用方在協程上調用.close()方法，或者沒有對協程引用而被垃圾回收程序回收時，這個協程才終止
        term = yield average
        total += term
        count += 1
        average = total/count
coro_avg = averager()
print(next(coro_avg))  #None
print(coro_avg.send(10)) #10.0
print(coro_avg.send(30)) #20.0
print(coro_avg.send(5))  #15.0


#16.4 預激程序的裝飾器
from functools import wraps

def coroutine(func):
    @wraps(func)
    def primer(*args,**kwargs):
        gen = func(*args,**kwargs)
        next(gen)
        return gen
    return primer

@coroutine
def averager():
    total = 0.0
    count = 0
    average = None
    while True:
        term = yield average
        total += term
        count += 1
        average = total/count

coro_avg = averager()
from inspect import getgeneratorstate
print(getgeneratorstate(coro_avg))  #GEN_SUSPENDED
print(coro_avg.send(10))     #10.0
print(coro_avg.send(30))    #20.0
print(coro_avg.send(5))     #15.0



#16.5 終止協程和異常處理
#例子 16-7 未處理的異常會導致協程終止
from functools import wraps
def coroutine(func):
    @wraps(func)
    def primer(*args,**kwargs):
        gen = func(*args,**kwargs)
        next(gen)
        return gen
    return primer

@coroutine
def averager():
    total = 0.0
    count = 0
    average = None
    while True:
        term = yield average
        total += term
        count += 1
        average = total/count
coro_avg = averager()
print(coro_avg.send(40))  #40.0
print(coro_avg.send(50))  #45.0
print(coro_avg.send(‘spam‘)) #TypeError: unsupported operand type(s) for +=: ‘float‘ and ‘str‘。此時，由於在協程裏沒有處理異常，協程會終止。如果試圖重新激活協程，會拋出
print(coro_avg.send(60))  #不會處理


# 例子16-8 在協程中處理異常代碼
class DemoException(Exception):
    ‘‘‘為這次演示定義的異常類型‘‘‘
def demo_exc_handling():
    print(‘-> coroutine started‘)
    while True:
        try:
            x = yield
        except DemoException:
            print(‘*** DemoException handled.Continuing...‘)
        else: #如果沒有異常，則顯示接收到的值
            print(‘->coroutine received:{!s}‘.format(x))
    raise RuntimeError(‘This line should never run.‘) #這一行永遠不會執行，因為只有未處理的異常才會終止那個無限循環

#激活和關閉demo_exc_handling，沒有異常
exc_coro = demo_exc_handling()
print(next(exc_coro))  #coroutine started
print(exc_coro.send(11)) #->coroutine received:11
print(exc_coro.send(22)) #->coroutine received:22
exc_coro.close()
from inspect import getgeneratorstate
print(getgeneratorstate(exc_coro))  #GEN_CLOSED

#把DemoException異常傳入demo_exc_handling不會導致協程中止
exc_coro = demo_exc_handling()
print(next(exc_coro))  #-> coroutine started
print(exc_coro.send(11)) #->coroutine received:11
print(exc_coro.throw(DemoException))  #*** DemoException handled.Continuing...
print(getgeneratorstate(exc_coro))  #GEN_SUSPENDED

#如果無法處理傳入的異常，協程會終止
exc_coro = demo_exc_handling()
print(next(exc_coro))  #-> coroutine started
print(exc_coro.send(11))
print(exc_coro.throw(ZeroDivisionError))
‘‘‘
Traceback (most recent call last):
  File "/Users/suren/PycharmProjects/fluentPython/kongzhiliucheng/xiecheng.py", line 172, in <module>
    print(exc_coro.throw(ZeroDivisionError))
  File "/Users/suren/PycharmProjects/fluentPython/kongzhiliucheng/xiecheng.py", line 145, in demo_exc_handling
    x = yield
ZeroDivisionError
‘‘‘
print(getgeneratorstate(exc_coro))  #GEN_CLOSED


#例子16-12 使用try/finally 塊在協程終止時執行操作
class DemoException(Exception):
    ‘‘‘為這次演示定義的異常類型‘‘‘
def demo_finally():
    print(‘-> coroutine started‘)
    try:
        while True:
            try:
                x = yield
            except DemoException:
                print(‘*** DemoException handled.Continuing.....‘)
            else:
                print(‘-> coroutine received:{!s}‘.format(x))
    finally:
        print(‘->coroutine ending‘)

# 激活和關閉demo_exc_handling，沒有異常
exc_coro = demo_finally() 
print(next(exc_coro))  #coroutine started  換行後打印 ->coroutine ending
print(exc_coro.send(11)) #->coroutine received:11  換行後打印 ->coroutine ending
print(exc_coro.send(22)) #->coroutine received:22  換行後打印 ->coroutine ending
exc_coro.close()
from inspect import getgeneratorstate
print(getgeneratorstate(exc_coro))  #GEN_CLOSED  換行後打印 ->coroutine ending

# 把DemoException異常傳入demo_exc_handling不會導致協程中止
exc_coro = demo_finally()
print(next(exc_coro))  #-> coroutine started  換行後打印 ->coroutine ending
print(exc_coro.send(11)) #->coroutine received:11  換行後打印 ->coroutine ending
print(exc_coro.throw(DemoException))  #*** DemoException handled.Continuing...  換行後打印 ->coroutine ending
print(getgeneratorstate(exc_coro))  #GEN_SUSPENDED  換行後打印 ->coroutine ending

#如果無法處理傳入的異常，協程會終止
exc_coro = demo_finally()
print(next(exc_coro))  #-> coroutine started  換行後打印 ->coroutine ending
print(exc_coro.send(11))
#print(exc_coro.throw(ZeroDivisionError))
‘‘‘
Traceback (most recent call last):
  File "/Users/suren/PycharmProjects/fluentPython/kongzhiliucheng/xiecheng.py", line 220, in <module>
    print(exc_coro.throw(ZeroDivisionError))
->coroutine ending
  File "/Users/suren/PycharmProjects/fluentPython/kongzhiliucheng/xiecheng.py", line 192, in demo_finally
    x = yield
ZeroDivisionError
->coroutine ending
‘‘‘
from inspect import getgeneratorstate
#print(getgeneratorstate(exc_coro))  #GEN_CLOSED  換行後打印 ->coroutine ending



#讓協程返回值
#例子16-14 
from collections import namedtuple

Result = namedtuple(‘Result‘,‘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 Result(count,average)

coro_avg = averager()
print(next(coro_avg)) #無產出
print(coro_avg.send(10)) #無產出
print(coro_avg.send(30)) #無產出
print(coro_avg.send(6.5)) #無產出
#print(coro_avg.send(None)) #StopIteration: Result(count=3, average=15.5)


#例子16-15
from collections import namedtuple
Result = namedtuple(‘Result‘,‘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 Result(count,average)




coro_avg = averager()
print(next(coro_avg)) #無產出
print(coro_avg.send(10)) #無產出
print(coro_avg.send(30)) #無產出
print(coro_avg.send(6.5)) #無產出
try:
    coro_avg.send(None)
except StopIteration as exc:
    result = exc.value
print(result)  #Result(count=3, average=15.5)

"""

【Python】【控制流程】【三】【協程】