在Spinbox上使用验证组件时的AttributeError

Question

我正在进行一个测试，编写一个脚本来验证一个spinbox，以便在一个更大的系统上实现它，但是我正在与python斗争，因为它警告我的Window类中没有spinbox属性。检查我的代码：

from Tkinter import *

class Window:

  def __init__(self, toplevel):

    self.spinbox = Spinbox(toplevel, from_ = 0, to = 10,
                           validate = 'all', validatecommand = self.validate)
    self.spinbox.pack()

  def validate(self):

    print self.spinbox.get()

root = Tk()
Window(root)
root.mainloop()

这就是它所犯的错误：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 1486, in __call__
    return self.func(*args)
  File "D:\DOCS\FILIPE\PROGRAMMING\PYTHON\Tkinter sandbox\01 - spinbox validate.
py", line 13, in validate
    print self.spinbox.get()
AttributeError: Window instance has no attribute 'spinbox'

有人能帮我这个忙吗？

Answer 1

如果将一些print语句添加到代码中：

class Window:
  def __init__(self, toplevel):
    print "A start", self, self.__dict__
    self.spinbox = Spinbox(toplevel, from_ = 0, to = 10,
                           validate = 'all', validatecommand = self.validate)
    self.spinbox.pack()
    print "A end", self, self.__dict__

  def validate(self):
    print "B", self, self.__dict__
    print self.spinbox.get()
#...

你得到的输出：

A start <__main__.Window instance at 0x7fe4f8deec20> {}
B <__main__.Window instance at 0x7fe4f8deec20> {}
Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1532, in __call__
    return self.func(*args)
  File "t.py", line 14, in validate
    print self.spinbox.get()
AttributeError: Window instance has no attribute 'spinbox'
A end <__main__.Window instance at 0x7fe4f8deec20> {'spinbox': <Tkinter.Spinbox instance at 0x7fe4f8e0da28>}

这意味着在构造函数中调用验证函数来验证初始值，此时还没有设置self.spinbox。您需要检查是否仍在构建或延迟设置validatecommand，如下所示：

self.spinbox = Spinbox(toplevel, from_ = 0, to = 10,
                       validate = 'all')
self.spinbox["validatecommand"] = self.validate
self.spinbox.pack()