嘗試在運行Tkinter的發送行程的行程之間通過管道發送任何內容時出現管道損壞錯誤

我玩弄Pipe和Process從multiprocessing模塊（Python的3.8）。我的初始程式如下所示：

from multiprocessing import Process, Pipe


class Process1(object):
    def __init__(self, pipe_out):
        self.pipe_out = pipe_out

        self.run()

    def run(self):
        try:
            while True:
                print("Sending message to process 2")
                self.pipe_out.send(["hello"])
        except KeyboardInterrupt:
            pass


class Process2(object):
    def __init__(self, pipe_in):
        self.pipe_in = pipe_in

        self.run()

    def run(self):
        try:
            while self.pipe_in.poll():
                request = self.pipe_in.recv()
                method = request[0]
                args = request[1:]

                try:
                    getattr(self, method   "_callback")(*args)
                except AttributeError as ae:
                    print("Unknown callback received from pipe", str(ae))

            print("Process 2 done with receiving")
        except KeyboardInterrupt:
            pass

    def hello_callback(self):
        print("Process 1 said hello")


class Controller(object):
    def __init__(self):
        pipe_proc1_out, pipe_proc2_in = Pipe()

        self.proc1 = Process(
            target=Process1,
            args=(pipe_proc1_out, )
        )

        self.proc2 = Process(
            target=Process2,
            args=(pipe_proc2_in, )
        )

    def run(self):
        try:
            self.proc1.start()
            self.proc2.start()

            while True:
                continue
        except KeyboardInterrupt:
            print("Quitting processes...")
            self.proc1.join(1)
            if self.proc1.is_alive():
                self.proc1.terminate()

            self.proc2.join(1)
            if self.proc2.is_alive():
                self.proc2.terminate()

            print("Finished")


def pipes():
    c = Controller()
    c.run()


if __name__ == "__main__":
    pipes()

我有一個Controller運行直到收到鍵盤中斷的實體。它還處理兩個行程Process1，Process2前者不斷發送，后者不斷接收。

上面的代碼是涉及復雜 GUI (PySide)、影像處理 (OpenCV) 和游戲引擎 (Panda3D) 的更大任務的骨架。所以我嘗試添加 Tkinter 作為 GUI 示例：

from multiprocessing import Process, Pipe
import tkinter as tk


class Process1(tk.Frame):
    def __init__(self, pipe_out):
        self.pipe_out = pipe_out

        self.setup_gui()
        self.run()

    def setup_gui(self):
        self.app = tk.Tk()
        lb1 = tk.Label(self.app, text="Message:")
        lb1.pack()
        self.ent1 = tk.Entry(self.app)
        self.ent1.pack()
        btn1 = tk.Button(self.app, text="Say hello to other process",
                         command=self.btn1_clicked)
        btn1.pack()

    def btn1_clicked(self):
        msg = self.ent1.get()
        self.pipe_out.send(["hello", msg])

    def run(self):
        try:
            self.app.mainloop()
        except KeyboardInterrupt:
            pass


class Process2(object):
    def __init__(self, pipe_in):
        self.pipe_in = pipe_in

        self.run()

    def run(self):
        try:
            while self.pipe_in.poll():
                request = self.pipe_in.recv()
                method = request[0]
                args = request[1:]

                try:
                    getattr(self, method   "_callback")(*args)
                except AttributeError as ae:
                    print("Unknown callback received from pipe", str(ae))

            print("Process 2 done with receiving")
        except KeyboardInterrupt:
            pass

    def hello_callback(self, msg):
        print("Process 1 say\""   msg   "\"")


class Controller(object):
    def __init__(self):
        pipe_proc1_out, pipe_proc2_in = Pipe()

        self.proc1 = Process(
            target=Process1,
            args=(pipe_proc1_out, )
        )

        self.proc2 = Process(
            target=Process2,
            args=(pipe_proc2_in, )
        )

    def run(self):
        try:
            self.proc1.start()
            self.proc2.start()

            while True:
                continue
        except KeyboardInterrupt:
            print("Quitting processes...")
            self.proc1.join(1)
            if self.proc1.is_alive():
                self.proc1.terminate()

            self.proc2.join(1)
            if self.proc2.is_alive():
                self.proc2.terminate()

            print("Finished")


def pipes():
    c = Controller()
    c.run()


if __name__ == "__main__":
    pipes()

請注意，當前 Tkinter 視窗只能在“父”行程通過鍵盤中斷時才能關閉。

每當我單擊按鈕并呼叫按鈕的命令時，我的程式都會進入錯誤狀態并顯示以下訊息：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\USER\Anaconda3\envs\THS\lib\tkinter\__init__.py", line 1705, in __call__
    return self.func(*args)
  File "C:\Users\USER\PycharmProjects\PythonPlayground\pipes_advanced.py", line 26, in btn1_clicked
    self.pipe_out.send(["hello", 1, 2])
  File "C:\Users\USER\Anaconda3\envs\THS\lib\multiprocessing\connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
  File "C:\Users\USER\Anaconda3\envs\THS\lib\multiprocessing\connection.py", line 280, in _send_bytes
    ov, err = _winapi.WriteFile(self._handle, buf, overlapped=True)
BrokenPipeError: [WinError 232] The pipe is being closed

起初我認為問題在于我從Entry.get()電話中收到的價值（我的 Tkinter 技能生疏了）。我列印msg并從小部件中獲取了文本。

接下來我嘗試將一個常量字串作為我通過管道發送的引數的值：

def btn1_clicked(self):
    self.pipe_out.send(["hello", "world"])

出現了同樣的錯誤。捕獲例外BrokenPipeError對我沒有任何好處（除非我想在管道損壞的情況下處理這種情況）。

如果我對程式的第一個版本（沒有 Tkinter）做同樣的事情，它就可以作業。這讓我相信我的問題來自于我集成 Tkinter 的方式。

uj5u.com熱心網友回復：

您遇到的問題是您輪詢管道，但檔案說：

民意調查（[超時]）

回傳是否有任何資料可供讀取。
如果未指定超時，則它將立即回傳。

在第一個示例中，它起作用是因為在啟動時Process1您立即將資料發送到管道：

    def run(self):
        try:
            while True:
                print("Sending message to process 2")
                self.pipe_out.send(["hello"])
        except KeyboardInterrupt:
            pass

并且您連續執行此操作，因此.poll將回傳True并且回圈Process2將繼續。

由于tkinter沒有任何東西立即發送到管道，它等待用戶單擊一個按鈕，當任何一個可能發生時，Process2已經呼叫poll并立即回傳False并且它甚至沒有啟動該回圈。如果您注意到，那么它也幾乎立即在終端中列印

“處理2完成接收”

要解決這個問題，似乎最簡單的方法是使用

while self.pipe_in.poll(None):

每個檔案意味著

“如果超時為 None，則使用無限超時。”

對于像用戶界面這樣的東西，這似乎是最合適的（至少從用戶的角度來看（或者我認為））所以基本上你的run方法Process2應該是這樣的：

    def run(self):
        try:
            while self.pipe_in.poll(None):
                request = self.pipe_in.recv()
                method = request[0]
                args = request[1:]

                try:
                    getattr(self, method   "_callback")(*args)
                except AttributeError as ae:
                    print("Unknown callback received from pipe", str(ae))

            print("Process 2 done with receiving")
        except (KeyboardInterrupt, EOFError):
            pass

也與問題無關，但似乎不需要從tk.Framein Process1（或objectin Process2（除非您確實需要使其與 Python2 兼容）），您幾乎可以繼承 from tk.Tk，這應該更容易實際使用它作為主視窗因為self將是Tk實體

標籤：Python 特金特 多处理 管道 python-多处理

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