具有第二功能延迟的多重处理

问题描述

我有一个将数据写入文本文件的功能，第二个功能是从同一文本文件中提取数据并显示图形.我想在第一个功能启动后数秒内启动第二个功能，并同时运行两个功能，直到两个功能都完成为止.通过这种方式，我可以获得实时图表.我在下面编写的代码同时启动了两个功能，但是第二个功能看不到任何文本文件.对于第二个函数，我需要一点时间来给第一个函数创建文本文件的时间.

I have a function that write data to a text file, a second function that pull data from the same text file and show a graph. I want to start the second function a few seconds after the first function is started and running both together till both completed. In this way I can get a live graph. The code I have written below starts the two functions simultaneously but the second function cannot see any text file. I need a bit of delay for the second function to give the time the first function to create the text file.

但是，因为第二个函数(live_graph)不仅需要从文本文件中提取数据，而且还需要从第一个函数中获取一些参数(例如图的标题)，所以我不确定这是否是正确的处理方法，似乎不可能从另一个功能中获得钥匙"；我得到密钥未定义".也许我还必须将参数也写入文本文件?

However because the second function (live_graph) needs not just pull data from the text file but also get some parameters (ex. title of the graph) from the 1st function I am not sure if this is the correct way to proceed, as it seems is not possible get a "key" from another function; I got "key not defined". Maybe I have to write to the text file also the parameters?

from multiprocessing import Process
import time

def writing():    
    numentries = 0
    for text in get_all(newlista, "sentence", "text"):

        if text.lower().startswith( key.lower().split(None, 1)[0] ):
            pass
        elif len(text) > 500:
            pass
        elif len(text) < 80:
            pass
        else:
            on_data(text)

            numentries += 1




  def live_graph():
  #pull data from text.txt
   time.sleep(5)


if __name__=='__main__':

 p1 = Process(target = writing)
 p1.start()
 p2 = Process(target = live_graph)
 p2.start()  

推荐答案

您要使用 multiprocessing.Queue

例如(来自文档):

from multiprocessing import Process, Queue

def f(q):
    q.put([42, None, 'hello'])

if __name__ == '__main__':
    q = Queue()
    p = Process(target=f, args=(q,))
    p.start()
    print q.get()    # prints "[42, None, 'hello']"
    p.join()

您可以像这样在代码中使用它:

You could use that in your code like this:

from multiprocessing import Process, Queue
import time


def writing(q):
    keep_running = True
    numentries = 0
    key = 'something, I assume'
    for text in get_all(newlista, "sentence", "text"):
        # Python lets you do nice comparisons like this,
        # which do what they look like. And make it more
        # obvious that you only want lines of length between
        # 80 and 500 characters
        if 80 < len(text) < 500:
            firstword = key.lower().split(None, 1)[0]
            if text.lower().startswith(firstword):               
                # Note: it is *essential* that in `on_data(text)`
                # after writing to your file you run `file.flush()`
                # or close the file, otherwise the data *may* be
                # buffered and hence, missing, when you go to read
                # the file
                on_data(text)
                q.put(keep_running)

    keep_running = False
    q.put(keep_running)

def live_graph(q):
    keep_running = True
    while keep_running:
        keep_running = q.get()
        # do the graph updates here


if __name__=='__main__':
 q = Queue()
 p1 = Process(target = writing, args=(q,))
 p1.start()
 p2 = Process(target = live_graph, args=(q,))
 p2.start()  

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