# asyncio
　　- Python3.4開始引入標準庫當中，內建對非同步io的支援
　　- asyncio本身是一個訊息迴圈
　　- 步驟：
　　　　- 1、建立訊息迴圈
　　　　- 2、把協成加進去
　　　　- 3、關閉

# asyncio非同步協成，簡單案例1
import threading
import asyncio

@asyncio.coroutine
# 使用協成
def hello():
    print('Hello world! (%s)' % threading.currentThread())
    print('Start...(%s)' % threading.currentThread())
    
 
yield from asyncio.sleep(5)
    print('Done...(%s)' % threading.currentThread())
    print('Hello again! (%s)' % threading.currentThread())
# 啟動訊息迴圈
loop = asyncio.get_event_loop()
# 定義任務
tasks = [hello(), hello()]
# asyncio使用wait等待tasks執行完畢
loop.run_until_complete(asyncio.wait(tasks))
# 關閉訊息尋混
loop.close()
 
'''
Hello world! (<_MainThread(MainThread, started 9272)>)
Start...(<_MainThread(MainThread, started 9272)>)
Hello world! (<_MainThread(MainThread, started 9272)>)
Start...(<_MainThread(MainThread, started 9272)>)
Done...(<_MainThread(MainThread, started 9272)>)
Hello again! (<_MainThread(MainThread, started 9272)>)
Done...(<_MainThread(MainThread, started 9272)>)
Hello again! (<_MainThread(MainThread, started 9272)>)
 
'''
# asyncio非同步用協成請求網路地址，案例2
import asyncio
@asyncio.coroutine
def wget(host):
    print('weget %s...' % host)
    # 非同步請求網路地址
    connect = asyncio.open_connection(host, 80)
    reader, writer = yield from connect
    header = 'GET / HTTP/1.0\r\nHost: %s\r\n\r\n' % host
    writer.writer(header.encode('utf-8'))
    yield from writer.drain()
    while True:
        line = yield from reader.readline()
        # http協議的換行使用\r\n
        if line ==b'\r\n':
            break
        print('%s header > %s' % (host, line.decode('utf-8').rstrip()))
    writer.close()
loop = asyncio.get_event_loop()
tasks = [wget(host) for host in ['www.sina.com.cn', 'www.sohu.com']]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()
'''
weget www.sina.com.cn...
weget www.sohu.com...
'''

# asyncio and await
　　- 為了更好的表示非同步io
　　- Python3.5引入
　　- 讓協成程式碼更簡潔
　　- 使用上，可以簡單的進行替換
　　　　- 用asyncio替換@asyncio.coroutine
　　　　- 用await替換yield from