python 并发编程 同步调用和异步调用 回调函数

 

 

提交任务的两张方式：

1.同步调用

2.异步调用

 

同步调用：提交完任务后，就在原地等待任务执行完后，拿到结果，再执行下一行代码

同步调用，导致程序串行执行

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
'''

 

异步调用：提交完任务后，不再原地等待任务执行完

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
'''

 

 

回调函数

可以为进程池或线程池内的每个进程或线程绑定一个函数，该函数在进程或线程的任务执行完毕后自动触发，并接收任务对象的返回值当作参数传给绑定的函数，该函数称为回调函数

 

add_done_callback() 
传的是要绑定的函数，还要在函数，func拿到的是一个future对象obj，需要用obj.result()拿到结果

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)

同步调用就是阻塞？

同步和阻塞没有关系，同步调用只是一种提交任务方式，同步提交完任务后，不管程序是计算密集型还是io密集型程序，它都会原地等待任务执行。