如何使Tkinter KeyRelease事件始终提供大写字母？

Question

当我尝试在Tkinter文本小部件上使用KeyRelease事件时，它有时在event.char中提供小写字符，但在文本小部件中显示大写字符。当我轻快地按下shift键，然后按下一个字母时，就会出现这种情况。如何使用Tkinter文本小部件上的KeyRelease事件可靠地捕获大小写正确的字符？

下面是我在我的MacBook专业版上测试的示例代码：

from Tkinter import *

class App:

    def __init__(self):

        # create application window
        self.root = Tk()

        # add frame to contain widgets
        frame = Frame(self.root, width=768, height=576, 
                      padx=20, pady=20, bg="lightgrey")
        frame.pack()

        # add text widget to contain text typed by the user
        self.text = Text(frame, name="typedText", bd="5", wrap=WORD, relief=FLAT)
        self.text.bind("<KeyRelease>", self.printKey)
        self.text.pack(fill=X)

    """
    printKey sometimes prints lowercase letters to the console, 
    but upper case letters in the text widget, 
    especially when I lightly and quickly press Shift and then some letter
    on my MacBook Pro keyboard
    """  
    def printKey(self, event):
        print event.char

    def start(self):
        self.root.mainloop()

def main():
    a = App()
    a.start()

if __name__ == "__main__":
    sys.exit(main())

Answer 1

发生的情况是，您在字母键之前释放了shift键。shift键是在插入字符时按下的，这就是为什么小工具会得到一个大写字符，但是当您的快捷键释放绑定被处理时，shift键已经被释放，所以您看到的是小写字符。

如果要打印正在插入的内容，请绑定到按键而不是释放键。

Answer 2

基于Bryan的洞察力，我修改了代码，它似乎可以工作：

from Tkinter import *
import string

class App:

  def __init__(self):

    # create application window
    self.root = Tk()

    # add frame to contain widgets
    frame = Frame(self.root, width=768, height=576, padx=20, pady=20, bg="lightgrey")
    frame.pack()

    # add text widget to contain text typed by the user
    self.text = Text(frame, name="typedText", bd="5", wrap=WORD, relief=FLAT)
    self.text.bind("<KeyPress>", self.printKey)
    self.text.pack(fill=X)

  """

  this correctly prints the letters when pressed (and does not print the Shift keys)

  """  
  def printKey(self, event):
    # Adapted from http://www.kosbie.net/cmu/fall-10/15-110/koz/misc-demos/src/keyEventsDemo.py
    ignoreSyms = [ "Shift_L", "Shift_R", "Control_L", "Control_R", "Caps_Lock" ]    
    if event.keysym not in ignoreSyms:
      print event.char

  def start(self):
    self.root.mainloop()

def main():
  a = App()
  a.start()

if __name__ == "__main__":
  sys.exit(main())