Question

关于如何为事件处理程序声明额外参数的New Mexico Tech website，提供了以下示例。

def __createWidgets(self):
    …
    self.cbList = []    # Create the checkbutton list
    for i in range(10):
        cb = tk.Checkbutton(self, …)
        self.cbList.append(cb)
        cb.grid( row=1, column=i)
        def handler(event, self=self, i=i):   ## 1
            return self.__cbHandler(event, i)
        cb.bind('<Button-1>', handler)
    …
def __cbHandler(self, event, cbNumber):
    …

备注## 1：这些行定义了一个期望的新函数处理程序三个论点。第一个参数是传递给all的Event对象事件处理程序，第二个和第三个参数将设置为它们的默认值 - 我们需要传递它的额外参数。

问题：

self=self中的def handler(...)争论是否需要通过 “自我”进入事件处理程序de __cbHandler(...)？默认情况下，“self”本身并不存在于事件处理程序中吗？
我写了一个测试代码来研究我的问题。用或如果没有参数self=self，则测试代码的工作方式相同。是否存在事件处理方案，其中声明self=self参数是强制/必要的？

测试代码：

#!/usr/bin/python3
# -*- coding: utf-8 -*-

try:
    import tkinter as tk # Python 3 tkinter modules
except ImportError:
    import Tkinter as tk # Python 2 tkinter modules

class NewListbox(tk.Frame):
    def __init__(self, parent, lb_values1, lb_values2):
        tk.Frame.__init__(self, parent)
        self.lb_values = tk.StringVar() 
        self.lb_values.set(lb_values1) 
        self.listbox = tk.Listbox(self, listvariable=self.lb_values)
        self.listbox.grid(row=2, column=0, sticky='nsew')

        # Having self=self and removing seems to make no difference.
        # self, appears to be pass on to the method def _update().
        def handler(event, self=self, values2=lb_values2): 
            return self._update(event, lb_values2)
        self.listbox.bind("<Button-1>", handler)

    def _update(self, event, newvalues):
        self.lb_values.set(newvalues)


class App(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        self.grid(row=0, column=0, sticky='nsew') 
        nlist1 = ['Peter', 'Scotty', 'Walter', 'Scott', 'Mary']
        nlist2 = ['Sarah', 'Jane', 'Oscar', 'Walley', 'Faith']
        self.lb = NewListbox(self, nlist1, nlist2)
        self.lb.grid(row=0, column=0, sticky='nsew')

if __name__ == '__main__':
    root = tk.Tk()
    app = App(root)
    app.mainloop()

原创方法（见下文）：

优点：易于实施。

实施成本：增加小部件的属性数量。

#!/usr/bin/python3
# -*- coding: utf-8 -*-

try:
    import tkinter as tk # Python 3 tkinter modules
except ImportError:
    import Tkinter as tk # Python 2 tkinter modules

class NewListbox(tk.Frame):
    def __init__(self, parent, lb_values1, lb_values2):
        tk.Frame.__init__(self, parent)
        self.lb_values = tk.StringVar() 
        self.lb_values.set(lb_values1) 
        self.lb_values2 = lb_values2   # create new attribute to store lb_values2
        self.listbox = tk.Listbox(self, listvariable=self.lb_values)
        self.listbox.grid(row=2, column=0, sticky='nsew')
        self.listbox.bind("<Button-1>", self._update)

    def _update(self, event):
        self.lb_values.set(self.lb_values2) #load new attribute.


class App(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        self.grid(row=0, column=0, sticky='nsew') 
        nlist1 = ['Peter', 'Scotty', 'Walter', 'Scott', 'Mary']
        nlist2 = ['Sarah', 'Jane', 'Oscar', 'Walley', 'Faith']
        self.lb = NewListbox(self, nlist1, nlist2)
        self.lb.grid(row=0, column=0, sticky='nsew')

if __name__ == '__main__':
    root = tk.Tk()
    app = App(root)
    app.mainloop()

为tkinter小部件事件处理程序声明额外的参数

0 个答案: