当在Python的多处理中与Kivy一起使用字符串共享内存时，会导致错误

Question

我尝试通过以下简单的Python代码使用字符串的共享内存，并且效果很好。

from multiprocessing import Value, Array, Process, Lock

def process1(array,  lock):
    with lock:
        buffer_data = str("z1111").encode("utf-8")
        array[0:len(buffer_data)] = buffer_data[:]
        
if __name__ == '__main__':
    array = Array('c', 35)
    lock = Lock()

    process_test1 = Process(target=process1, args=[array, lock], daemon=True)
    
    process_test1.start()
    process_test1.join()
    
    print(array[:].decode("utf-8"))
    print("process ended")

接下来，我尝试使用名为 Kivy 的 GUI 库实现

数字共享内存，效果也很好。

from multiprocessing import Process, Value, set_start_method, freeze_support, Lock

kvLoadString=("""
<TextWidget>:
    BoxLayout:
        orientation: 'vertical'
        size: root.size

        Button:
            id: button1
            text: "start"
            font_size: 48
            on_press: root.buttonClicked()
        Label:
            id: lab
            text: 'result'
""")

def start_process(count,lock):
    process_test = Process(target=p_test, args=[count,lock], daemon=True)
    process_test.start()
    return process_test

def p_test(count,lock):
    i = 0
    while True:
        print(i)
        i = i + 1
        with lock:
            count.value = i

if __name__ == '__main__':
    freeze_support() 
    from kivy.app import App
    from kivy.uix.widget import Widget
    from kivy.lang import Builder

    from kivy.uix.checkbox import CheckBox
    from kivy.uix.spinner import Spinner
    from kivy.properties import StringProperty,NumericProperty,ObjectProperty, BooleanProperty
    from kivy.core.window import Window
    from kivy.uix.boxlayout import BoxLayout
    from kivy.uix.popup import Popup
    from kivy.uix.treeview import TreeView, TreeViewLabel, TreeViewNode
    from kivy.uix.label import Label
    from kivy.uix.textinput import TextInput
    from kivy.uix.progressbar import ProgressBar
    from kivy.uix.button import Button

    set_start_method('spawn')


    class TestApp(App):
        def __init__(self, **kwargs):
            super(TestApp, self).__init__(**kwargs)
            self.title = 'testApp'

        def build(self):
            return TextWidget()

    class TextWidget(Widget):
        def __init__(self, **kwargs):
            super(TextWidget, self).__init__(**kwargs)
            self.process_test = None
            self.proc = None

            # shared memory
            self.count = Value('i', 0)
            self.lock = Lock()

        def buttonClicked(self):
            if self.ids.button1.text == "start":
                self.proc = start_process(self.count,self.lock)
                self.ids.button1.text = "stop"
            else:
                if self.proc:
                    self.proc.kill()
                self.ids.button1.text = "start"
                self.ids.lab.text = str(self.count.value)

    Builder.load_string(kvLoadString)
    TestApp().run()

但是，我没有

成功地将Kivy与字符串共享内存一起使用

，如下所示。

from multiprocessing import Array,Process, Value, set_start_method, freeze_support, Lock
import math

kvLoadString=("""
<TextWidget>:
    BoxLayout:
        orientation: 'vertical'
        size: root.size

        Button:
            id: button1
            text: "start"
            font_size: 48
            on_press: root.buttonClicked()
        Label:
            id: lab
            text: 'result'
""")

def start_process(array,lock):
    process_test = Process(target=p_test, args=[array,lock], daemon=True)
    process_test.start()
    return process_test

def p_test(array,lock):
    with lock:
        buffer_data = str("z1111").encode("utf-8")
        array[0:len(buffer_data)] = buffer_data[:]
        print(array.decode("utf-8"))

if __name__ == '__main__':
    freeze_support() 
    from kivy.app import App
    from kivy.uix.widget import Widget
    from kivy.lang import Builder

    from kivy.uix.checkbox import CheckBox
    from kivy.uix.spinner import Spinner
    from kivy.properties import StringProperty,NumericProperty,ObjectProperty, BooleanProperty
    from kivy.core.window import Window
    from kivy.uix.boxlayout import BoxLayout
    from kivy.uix.popup import Popup
    from kivy.uix.treeview import TreeView, TreeViewLabel, TreeViewNode
    from kivy.uix.label import Label
    from kivy.uix.textinput import TextInput
    from kivy.uix.progressbar import ProgressBar
    from kivy.uix.button import Button

    set_start_method('spawn')


    class TestApp(App):
        def __init__(self, **kwargs):
            super(TestApp, self).__init__(**kwargs)
            self.title = 'testApp'

        def build(self):
            return TextWidget()

    class TextWidget(Widget):
        def __init__(self, **kwargs):
            super(TextWidget, self).__init__(**kwargs)
            self.process_test = None
            self.proc = None

            # shared memory
            self.array = Array('c', 35)
            self.lock = Lock()

        def buttonClicked(self):
            if self.ids.button1.text == "start":
                self.proc = start_process(self.array,self.lock)
                self.ids.button1.text = "stop"
            else:
                if self.proc:
                    self.proc.kill()
                self.ids.button1.text = "start"
                self.ids.lab.text = self.array.decode("utf-8")

    Builder.load_string(kvLoadString)
    TestApp().run()

错误信息如下。如何避免这样的错误？

Traceback (most recent call last):
  File "C:\Users\taichi\Documents\Winpython64-3.9.10.0\WPy64-39100\python-3.9.10.amd64\lib\multiprocessing\process.py", line 315, in _bootstrap
    self.run()
  File "C:\Users\taichi\Documents\Winpython64-3.9.10.0\WPy64-39100\python-3.9.10.amd64\lib\multiprocessing\process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\taichi\Desktop\test.py", line 29, in p_test
    print(array.decode("utf-8"))
AttributeError: 'SynchronizedString' object has no attribute 'decode'

Answer 1

s = bytes.join(b'', [c for c in array if c != b'\x00']).decode('utf-8')