Question

此示例成功允许仅输入数字，但在输入第一个字符后，它不允许您删除它。为什么会这样？

import Tkinter as tk

class window2:
    def __init__(self, master1):
        self.panel2 = tk.Frame(master1)
        self.panel2.grid()
        self.button2 = tk.Button(self.panel2, text = "Quit", command = self.panel2.quit)
        self.button2.grid()
        vcmd = (master1.register(self.validate),
                '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')
        self.text1 = tk.Entry(self.panel2, validate = 'key', validatecommand = vcmd)
        self.text1.grid()
        self.text1.focus()

    def validate(self, action, index, value_if_allowed,
                       prior_value, text, validation_type, trigger_type, widget_name):
        if text in '0123456789.-+':
            try:
                float(value_if_allowed)
                return True
            except ValueError:
                return False
        else:
            return False

root1 = tk.Tk()
window2(root1)
root1.mainloop()

Answer 1

因为删除该字符会留下""，根据您的规则，这不是可接受的条目：

>>> "" in '0123456789.-+'
True

但

>>> float("")
Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    float("")
ValueError: could not convert string to float:

限制Tkinter Entry小部件中的值：为什么我不能删除第一个字符？

1 个答案: