多处理管道 send() 块

Question

根据 Python 文档，只有recv()块而不是send(). 我写了以下代码试图制作一个 GUI 数独游戏。我这样做的方式是，即使tkinter正在执行其mainloop. 但是，在测试运行期间，我发现如果我在游戏更新时关闭窗口，则pipe.send()开始阻止（我使用 CPython 分析器发现了这一点。）谁能告诉我原因，如果可能，如何解决这个问题问题？

产生问题：在脚本更新时关闭弹出的窗口。也就是说，在将一些数字打印到控制台时关闭窗口。

我的系统：macOS Sierra 10.12.5

import multiprocessing as mp
import threading
import random
import time
try:
    import tkinter as tk  # Python3
except ImportError:
    import Tkinter as tk  # Python2

class VisualizedBoard:
    def __init__(self,input_string,pipe):
        '''input_string: a string has a length of at least 81 that represent the board from top-left to bottom right.
        empty cell is 0'''

        self.update_scheduled=False
        self.pipe=pipe

        # create board
        self.root = tk.Tk()
        self.canvas = tk.Canvas(self.root, width=500, height=500)
        self.canvas.create_rectangle(50, 50, 500, 500, width=2)
        for i in range(1, 10):
            self.canvas.create_text(25 + 50 * i, 30, text=str(i))
            self.canvas.create_text(30, 25 + 50 * i, text=str(i))
            self.canvas.create_line(50 + 50 * i, 50, 50 + 50 * i, 500, width=2 if i % 3 == 0 else 1)
            self.canvas.create_line(50, 50 + 50 * i, 500, 50 + 50 * i, width=2 if i % 3 == 0 else 1)

        for i in range(81):
            if input_string[i] != '0':
                self.canvas.create_text(75 + 50 * (i // 9), 75 + 50 * (i % 9), tags=str((i//9+1,i%9+1)).replace(' ',''),text=input_string[i], fill='black')

        self.canvas.pack()
        self.root.attributes('-topmost', True)

        self.root.geometry('550x550+%d+%d' % ((self.root.winfo_screenwidth() - 550) // 2, (self.root.winfo_screenheight() - 550) // 2))
        self.root.wm_protocol('WM_DELETE_WINDOW',lambda :(self.root.destroy()))
        threading.Thread(target=self.listen, args=()).start()
        self.root.mainloop()


    def update(self,coordinate,value,color='magenta'):
        """
                :parameter coordinate: a tuple (x,y)
                :parameter value: single digit
                :returns: None
        """
        try:
            assert isinstance(coordinate,tuple)
        except AssertionError:
            print('Update Failed. Coordinate should be a tuple (x,y)')

        coordinate_tag=str(coordinate).replace(' ','')
        self.canvas.delete(coordinate_tag)
        if value != 0 and value != '0':
            self.canvas.create_text(25+50*coordinate[0],25+50*coordinate[1],tags=coordinate_tag,text=str(value),fill=color)

        self.postponed_update()

        #self.canvas.update()

    def postponed_update(self):
        if not self.update_scheduled:
            self.canvas.after(50,self.scheduled_update)
            self.update_scheduled=True

    def scheduled_update(self):
        self.canvas.update()
        self.update_scheduled=False

    def new_board(self,input_string):
        self.root.destroy()
        return VisualizedBoard(input_string,self.pipe)

    def listen(self):
        try:
            while True:
                msg=self.pipe.recv()
                self.update(*msg)
        except EOFError:
            self.pipe.close()
            tk.Label(self.root,text='Connection to the main script has been closed.\nIt is safe to close this window now.').pack()
        except Exception as m:
            self.pipe.close()
            print('Error during listing:',m)



class BoardConnection:
    def __init__(self,input_string):
        ctx = mp.get_context('spawn')
        self.receive,self.pipe=ctx.Pipe(False)
        self.process=ctx.Process(target=VisualizedBoard,args=(input_string,self.receive))
        self.process.start()

    def update(self,coordinate,value,color='magenta'):
        """
        :parameter coordinate: a tuple (x,y)
        :parameter value: single digit
        :returns: None
        """
        self.pipe.send((coordinate,value,color))

    def close(self):
        self.pipe.close()
        self.process.terminate()





if __name__ == "__main__":
    b=BoardConnection('000000000302540000050301070000000004409006005023054790000000050700810000080060009')
    start = time.time()
    for i in range(5000): #test updating using random numbers
        b.update((random.randint(1, 9), random.randint(1, 9)), random.randrange(10))
        print(i)
    print(time.time() - start)

Answer 1

PythonPipe是 OS 无名管道之上的抽象。

操作系统管道通常作为内核中特定大小的内存缓冲区来实现。默认情况下，如果缓冲区填满，则下一次发送/写入调用将被阻塞。

如果您希望能够在没有消费者使用数据的情况下继续发布数据，您应该使用 amultiprocessing.Queue或asyncio设施。

它multiprocessing.Queue使用“无限”缓冲区和线程将数据推送到操作系统管道中。如果管道变满，调用者将继续运行，因为发布的数据将堆积在Queue缓冲区中。

IIRC，asyncio 设置管道O_NONBLOCK标志并等待管道被消耗。附加消息存储在“无限”缓冲区中，对于multiprocessing.Queue.