如何从 Tkinter GUI 中删除警告标签

Question

我有一些代码想要检查用户输入到两个 tk 条目的有效性，如果输入的是字母而不是数字，它会以红色文本发布警告 - 这是正确执行的。我希望它做的是在用户插入数字后删除红色文本 - 目前红色 ValueError 文本仍然存在，如果两个条目都是数字，我希望它在按下按钮后消失。

代码

print('\n'*3)
import tkinter as tk


root = tk.Tk()
pw_low = 0.01
pw_high = 30.0

lab1 = tk.Label(root, text="Pulse Width Start (\u03bcS):").grid(row = 0)
start_pw = tk.StringVar()
entry1 = tk.Entry(root, width=20, textvariable = start_pw).grid(row = 0, column = 1)
start_pw.set(pw_low)

lab2 = tk.Label(root, text="Pulse Width End (\u03bcS):").grid(row = 1)
end_pw = tk.StringVar()
entry2 = tk.Entry(root, width=20, textvariable = end_pw).grid(row = 1, column = 1)
end_pw.set(pw_high)


def getPWrange():
    try:
        user_start_pw_num = float(start_pw.get())
    except ValueError:
        answer_label.config(text = 'You must enter an integer or decimal number', fg = 'red')
    try:
        user_end_pw_num = float(end_pw.get())
        user_pw_range = [user_start_pw_num, user_end_pw_num ]
        print('user_pw_range: ',user_pw_range)
    except ValueError:
        answer_label.config(text = 'You must enter an integer or decimal number', fg = 'red')


button = tk.Button(root, text="Range", command = getPWrange)
button.grid(row = 2, column = 3)
answer_label = tk.Label(root, text = '')
answer_label.grid(row = 3)

root.mainloop()

不满意的解决方案

在添加数字后添加标签 destroy 确实会删除标签，但是如果在此之后输入字母，则不会显示警告错误，而是得到回溯

def getPWrange():
    try:
        user_start_pw_num = float(start_pw.get())
    except ValueError:
        answer_label.config(text = 'You must enter an integer or decimal number', fg = 'red')
        answer_label.after(2000, answer_label.destroy)
    try:
        user_end_pw_num = float(end_pw.get())
        user_pw_range = [user_start_pw_num, user_end_pw_num ]
        print('user_pw_range: ',user_pw_range)
    except ValueError:
        answer_label.config(text = 'You must enter an integer or decimal number', fg = 'red')


Traceback (most recent call last):
  File "/Users/.../opt/anaconda3/lib/python3.7/tkinter/__init__.py", line 1705, in __call__
    return self.func(*args)
  File "/Users/.../Desktop/tk_gui_grid/t6.py", line 24, in getPWrange
    answer_label.config(text = 'You must enter an integer or decimal number', fg = 'red')
  File "/Users/.../opt/anaconda3/lib/python3.7/tkinter/__init__.py", line 1485, in configure
    return self._configure('configure', cnf, kw)
  File "/Users/.../opt/anaconda3/lib/python3.7/tkinter/__init__.py", line 1476, in _configure
    self.tk.call(_flatten((self._w, cmd)) + self._options(cnf))
_tkinter.TclError: invalid command name ".!label3"

期望输出

如果所有条目均有效，则 answer_label 将被删除。

Answer 1

去掉try块中标签的文字即可：

try:
    user_start_pw_num = float(start_pw.get())
    user_end_pw_num = float(end_pw.get())

    user_pw_range = [user_start_pw_num, user_end_pw_num ]
    print('user_pw_range: ',user_pw_range)

    answer_label.config(text='')

except ValueError:
    answer_label.config(text='You must enter an integer or decimal number', fg='red')

将两个 try-except 块合并为一个。

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