進程不會在python中啓動

Question

我正在試圖創建一個簡單的python腳本來學習如何使用多處理。我想在後臺創建一個進程，它將生成虛擬數據並將其放入隊列中，同時用戶仍然可以輸入命令。

這裏是我的代碼：

from multiprocessing import Process 
from multiprocessing import Queue 
import random 
import os 

global run 

def waitForStart(q): 
    global run 
    print("(h for help)") 
    while run == 0: 
     response = input("Enter a command: \n") 

     if response == "h": 
      print("h - help\ns - select a profile\no - output a profile\nd - 
download a profile\nd - display selected profile\nr - run selected profile") 

     if response == "r": 
      run = 1 
      beginInterface(q) 
      print("r") 

def generateData(q): 
    data = random.randint(0,100) 
    q.put(data) 

def beginControl(q): 
    print("bcontrol") 
    while run == 1: 
     generateData(q) 
     displayData() 
     adjustOutputs() 
     logData() 
    print("Finished Control") 

def beginInterface(q): 
    global run 
    p.start() 
    print("binterface") 
    while run == 1: 
     response = input("pause? (y/n)\n") 
     print(p.is_alive()) 
     if response == 'y': 
      run = 0 

def displayData(): 
    print(q.get()) 

run = 0 
q = Queue() 
p = Process(target=beginControl , args=(q,)) 
waitForStart(q) 

我很困惑，因爲is_alive調用返回false即使p.start（）被調用的幾行之前。

Answer 1

由於您有兩個進程run在第二個是0並且永遠不會進入循環。要在主流程和第二個流程之間進行溝通，請使用Pipe or a Queue。

重要的注意，如果在Win不要忘了補充：

if __name__ == "__main__": 

See reason here.

另一件事，你永遠傳遞隊列displayData，編輯：

def displayData(q): 
    print(q.get()) 

而且，我認爲你真正想要的是一個線程，因爲這段代碼會將進程置於一個無限循環中。

這不正是你的代碼，但它傳達的理念是：

from multiprocessing import Process 
from multiprocessing import Queue, Pipe 
import random 
import time 


def waitForStart(q): 
    global run 
    print("(h for help)") 
    while True: 
     response = input("Enter a command: \n") 

     if response == "h": 
      print("h - help" 
        "s - select a profile" 
        "o - output a profile" 
        "d - download a profile" 
        "d - display selected profile" 
        "r - run selected profile") 

     if response == "r": 
      run = 1 
      beginInterface() 
      print("r") 


def generateData(q): 
    data = random.randint(0,100) 
    q.put(data) 


def beginControl(q): 
    print("bcontrol") 
    while q.empty(): 
     generateData(q) 
     displayData(q) 
     #adjustOutputs() 
     #logData() 
    print("Finished Control") 


def beginInterface(): 
    p.start() 
    print("binterface") 
    while True: 
     print(p.is_alive()) 
     time.sleep(1) 
     q.put('DIE!') 
     p.join() 
     exit() 


def displayData(q): 
    data = q.get() 
    if data != 'DIE!': 
     print(data) 


if __name__ == "__main__": 
    q = Queue() 
    pip = Pipe() 
    p = Process(target=beginControl, args=(q,)) 
    waitForStart(q)