python 並發編程 同步調用和異步調用 回調函數

 

 

提交任務的兩張方式：

1.同步調用

2.異步調用

 

同步調用：提交完任務后，就在原地等待任務執行完后，拿到結果，再執行下一行代碼

同步調用，導致程序串行執行

from concurrent.futures import ThreadPoolExecutor
import time
import random


def la(name):
    print("%s is 正在拉" % name)
    time.sleep(random.randint(1,3))
    res = random.randint(1,10) * "#"
    return {"name":name,"res":res}

def weigh(shit):
    name = shit["name"]
    size = len(shit["res"])
    print("%s 拉了《%s》kg" %(name,size))

if __name__ == "__main__":
    pool = ThreadPoolExecutor(13)

    shit1 = pool.submit(la,"mike").result()
    weigh(shit1)
    shit2 = pool.submit(la,"peter").result()
    weigh(shit2)
    shit3 = pool.submit(la,"jack").result()
    weigh(shit3)

'''
mike is 正在拉
mike 拉了《2》kg
peter is 正在拉
peter 拉了《9》kg
jack is 正在拉
jack 拉了《4》kg
'''

 

異步調用：提交完任務后，不再原地等待任務執行完

from concurrent.futures import ThreadPoolExecutor
import time
import random


def la(name):
    print("%s is 正在拉" % name)
    time.sleep(random.randint(1,3))
    res = random.randint(1,10) * "#"
    return weigh({"name":name,"res":res})

def weigh(shit):
    name = shit["name"]
    size = len(shit["res"])
    print("%s 拉了《%s》kg" %(name,size))

if __name__ == "__main__":
    pool = ThreadPoolExecutor(13)

    pool.submit(la,"mike")
    pool.submit(la,"peter")
    pool.submit(la,"jack")

'''
mike is 正在拉
peter is 正在拉
jack is 正在拉
mike 拉了《3》kg
jack 拉了《8》kg
peter 拉了《1》kg
'''

 

 

回調函數

可以為進程池或線程池內的每個進程或線程綁定一個函數，該函數在進程或線程的任務執行完畢后自動觸發，並接收任務對象的返回值當作參數傳給綁定的函數，該函數稱為回調函數

 

add_done_callback() 
傳的是要綁定的函數，還要在函數，func拿到的是一個future對象obj，需要用obj.result()拿到結果

from concurrent.futures import ThreadPoolExecutor
import time
import random


def la(name):
    print("%s is 正在拉" % name)
    time.sleep(random.randint(1,3))
    res = random.randint(1,10) * "#"
    return {"name": name, "res": res}

def weigh(shit):
    shit = shit.result()
    name = shit["name"]
    size = len(shit["res"])
    print("%s 拉了《%s》kg" %(name,size))

if __name__ == "__main__":
    pool = ThreadPoolExecutor(13)

    pool.submit(la,"mike").add_done_callback(weigh)
    pool.submit(la,"peter").add_done_callback(weigh)
    pool.submit(la,"jack").add_done_callback(weigh)

同步調用就是阻塞？

同步和阻塞沒有關系，同步調用只是一種提交任務方式，同步提交完任務后，不管程序是計算密集型還是io密集型程序，它都會原地等待任務執行。