python thread pool practical summary

Two methods submit and map the thread pool

from concurrent.futures import ThreadPoolExecutor
import time

#


def sayhello(a):
    time.sleep(2)
    return "hello: "+a


def main():
    seed = ["a","b","c"]
    # 不使用线程
    start1 = time.time()
    for each in seed:
        t1 = sayhello(each)
        print(T1) 
    END1 = the time.time ()
     Print ( " TIME1: " + STR (end1- Start1))
     Print ( ' ------------------ Submit ---- ------------------ ' )
     # thread pool usage submit 
    # 1 value is stored in the first list 
    # 2 takes the return value in the traversal list 
    # 3 will be acquired traverse the result is stored in the list 
    start2 = the time.time () 
    LST = [] 
    result_lst = [] 
    with the ThreadPoolExecutor ( . 3 ) AS Executor:
         for each in  SEED:
            T2 =executor.submit (sayHello, each) 
            lst.append (T2) 
        for I in LST:
             Print (i.result ()) 
            result_lst.append (i.result ()) 
        Print (result_lst) 
    end2 = the time.time ()
     Print ( " TIME2: " + STR (end2- start2)) 

    Print ( ' --------------- Map ------------------- --- ' )
     # usage map of the thread pool 
    # parameters of the map: iterator 
    # map the return value: generator 
    # 1, generator acquires (or directly attached to force transducers list) 
    # 2, traversal value
    #3, the traversal results into a new list 
    map_lst = [] 
    start3 = the time.time () 
    with the ThreadPoolExecutor ( 3 ) AS executor1: 
        T3 = executor1.map (sayHello, SEED)
         for T in T3: 
            map_lst.append (T ) 
        Print (map_lst) 
    END3 = the time.time ()
     Print ( " time3: " + STR (end3- start3)) 


IF  the __name__ == ' __main__ ' : 
    main ()

the difference

the Map:
 1 , submitted by the task function is the same as
 2 parameters: only need to submit one objective function, parameter objective function in an iterator (lists, dictionaries) 
the Submit:
 1 , submitted by the task function is not the same, or abnormalities that may occur in the process of execution (using a process map to identify problems in the implementation of a direct throw an error)
 2 , parameter: submit every parameter required to submit an objective function and the corresponding 

results: 
map can guarantee the order of output, submit output the order is chaos