python - 在删除之前检查小部件是否存在于 tkinter 中

Question

我正在使用下拉菜单创建多个小部件。我想在删除小部件之前检查它是否存在(从下拉菜单中的先前选择)。我正在使用以下代码:

self.ndim_options, self.ndim_options_var = self.DropdownMenuCommand(("1","2","3"),'-',"Number of indirect dimensions","-")

def DropdownMenuCommand(self,options,status,name,row):

    if row == "-":
      row = self.row

    optionLabel = tk.Label(self.frame, bg='turquoise')
    optionLabel["text"] = name
    optionLabel.grid(row=row, column=0, sticky='w')
    var = tk.StringVar(self)
    var.set(status)
    w = tk.OptionMenu(self.frame, var, *options, command = self.setdimensionproperties)
    w.config(bg = 'paleturquoise')
    w["menu"].config(bg = 'paleturquoise')
    w.grid(row=row, column=1)
    self.row += 1
    return w, var

def setdimensionproperties(self,val):
    row = self.RowEnd

    if val == "3":  #Set parameters for a 4D (3 indirect dimensions)

      #Remove any existing weighting functions
      if self.weightingFuncNameDim2.winfo_exists():
        self.weightingFuncNameDim2.grid_remove()

      self.weightingFuncNameDim2, self.weightingFuncNameDim2_var = self.DropdownMenu(("sinebell","gaussian", "sinebell2"),'-', "Weighting function dimension 2",row)

但是，如果尚未创建小部件，我会收到一个属性错误:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1413, in __call__
    return self.func(*args)
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 3141, in __call__
    self.__callback(self.__value, *args)
  File "test.py", line 224, in setdimensionproperties
    if self.weightingFuncNameDim2.winfo_exists():
AttributeError: Window instance has no attribute 'weightingFuncNameDim2'

理想情况下，如果小部件存在，我希望 if 语句返回 1，如果不存在，则返回 0，这就是我的想法 .winfo_exists( ) 做到了。我怎样才能解决这个错误？另外，如何确保 .grid_remove 删除小部件和标签？

Answer 1

我看到三种可能的解决方案。按优先顺序:

1. 将 self.weightingFuncNameDim2 = None 添加到您的类的 __init__ 方法中，并将您的 if 条件更改为 if self.weightingFuncNameDim2 不是 None 和 self.weightingFuncNameDim2.winfo_exists():

2. 将条件更改为 if hasattr(self, "weightingFuncNameDim2") and self.weightingFuncNameDim2.winfo_exists():

3. 将您的 if block 放在捕获并忽略 AttributeErrors 的 try-except block 中。