如何在python中引用类内的Tkinter小部件

Question

我创建了两个列表框小部件，在其中选择一个项目，然后按下面的按钮将项目移动到另一个。在

这工作得非常好，但是我想重用容器框架，因为这两个框架的布局是相同的（除了标题标签和按下按钮时的功能）。所以我把除了button函数之外的所有代码都移到了一个类“ColumnSelector”。在

但是，要将数据从一个“ColumnSelector”移动到另一个，我需要引用实例中的列表框。下面是我想做的事情的结构，但我不确定这是否可能。在

我尝试过其他一些方法，比如在ColumnSelector类之外创建listbox并传递给它，但是这样做也遇到了问题。在

在其他类的实例中引用小部件的最佳方法是什么？在

    # Data to be included in second listbox widget
    startingSelection = ('Argentina', 'Australia', 'Belgium', 'Brazil', 'Canada', 'China', 'Denmark')

    # Two functions performed by the ColumnSelectors
    def removeSelected(*args):
        idxs = selectedColumns.listBox.curselection() # <- Does not reference correctly
        if len(idxs)>=1:
            for n in reversed(range(len(idxs))):
                idx = int(idxs[n])
                item = selectedColumns.listBox.get(idx)
                selectedColumns.listBox.delete(idx)
                availableColumns.listBox.insert(availableColumns.listBox.size(), item)

    def addSelected(*args):
        idxs = availableColumns.listBox.curselection() #<- Does not reference correctly
        if len(idxs)>=1:
            for n in reversed(range(len(idxs))):
                idx = int(idxs[n])
                item = availableColumns.listBox.get(idx)
                availableColumns.listBox.delete(idx)
                selectedColumns.listBox.insert(selectedColumns.listBox.size(), item)

    # Create ColumnSelectors, pass heading title and function to perform
    selectedColumns = ColumnSelector(self, "Columns to include in export", (), removeSelected).grid(column=0, row=0, sticky=(N,W))
    availableColumns = ColumnSelector(self, "Available Columns", startingSelection, addSelected).grid(column=1, row=0, sticky=(N,W))

class ColumnSelector(ttk.Frame):
    def __init__(self, parent, labelText, startingSelection, function ):
        listBox = Listbox(self, height=5, selectmode='multiple')
        removeColumnsButton = ttk.Button(self, text="Move", command=function)
        #(etc...)

Answer 1

What would be the best way to reference widgets inside instances of other classes?

我认为最常见的用例是无限次地重用一个对象，因为它看起来像是在试图处理一些在框架内设置的列表框。在这种情况下，我认为您应该在子类中放入尽可能多的可重复代码，并在其中创建一个方法来返回您想要的结果。当您在主类中创建子类的实例时，您可以在需要时访问它的方法（即selectedColumns.get_all_listbox_values()）。在

需要记住的一点是，如果创建实例并将其网格化在同一行上，则实例将无法正常工作：

否

selectedColumns = ColumnSelector(self, "Columns to include in export", (), removeSelected).grid(column=0, row=0, sticky=(N,W))
selectedColumns.get_all_listbox_values()
>>> AttributeError: 'NoneType' object has no attribute 'get_all_listbox_values'

是

^{2}$

下面是一个设置脚本的方法示例。有一个主类（App）和另一个继承自Frame（MyEntry）的类，可以在App中多次使用。在App类中有一个按钮，它打印出MyEntry中计算两个值的方法的结果。希望它能帮助您对构建代码有一些想法。在

class App(Frame):
    '''the main window class'''
    def __init__(self, parent):
        Frame.__init__(self, parent)

        # create instances of MyEntry, passing whatever operators as args
        # we can make as many of these instances as we need in just a couple of lines
        # and it retains readability
        self.divide = MyEntry(self, '/')
        self.multiply = MyEntry(self, '*')

        self.divide.pack()
        self.multiply.pack()

        Button(self, text='Calculate', command=self._print_result).pack()

    def _print_result(self):
        '''print the return of the calculate method from the instances of
        the MyEntry class'''
        print self.divide.calculate()
        print self.multiply.calculate()

class MyEntry(Frame):
    '''creates two entries and a label and has a method to calculate
    the entries based on an operator'''
    def __init__(self, parent, operator): # include the operator as an arg
        Frame.__init__(self, parent)

        # make an instance variable from the operator to access it between methods
        self.operator = operator

        # make two entries
        self.num1 = Entry(self)
        self.num2 = Entry(self)

        # grid the entries and a label which contains the operator
        self.num1.grid(row=0, column=0)
        Label(self, text=self.operator).grid(row=0, column=1)
        self.num2.grid(row=0, column=2)

    def calculate(self):
        '''return the value of the two entries based on the operator specified'''
        if self.operator is '/':
            return int(self.num1.get()) / int(self.num2.get())
        elif self.operator is '*':
            return int(self.num1.get()) * int(self.num2.get())
        else:
            return

root = Tk()
App(root).pack()
mainloop()