如何用可调用的 class object 回调处理程序替换 lambda 回调处理程序？

Question

我的以下问题与 Mark Lutz 第 4 版Programming Python的示例 8-10 有关。 该示例是关于创建一个简单按钮栏，用于启动对话框演示并在stdout中返回这些对话框调用的值。

对话表如下所示：

#dialogTable.py

from tkinter.filedialog     import askopenfilename
from tkinter.colorchooser   import askcolor
from tkinter.messagebox     import askquestion, showerror
from tkinter.simpledialog   import askfloat

demos = {
    'Open': askopenfilename,
    'Color': askcolor,
    'Query': lambda: askquestion('Warning', 'You typed "rm *"\nConfirm?'),
    'Error': lambda: showerror('Error!', "He's dead, Jim"),
    'Input': lambda: askfloat('Entry', 'Enter credit card number')
}

下面的代码创建按钮栏并使它们起作用。 我的问题与这部分有关：

from tkinter import *
from dialogTable import demos       # button callback handlers
from quitter import Quitter         # attach a quit object to me

class Demo(Frame):
    def __init__(self, parent=None, **options):
        Frame.__init__(self, parent)
        self.pack()
        Label(self, text="Basic demos").pack()
        for key in demos:
            func = (lambda key=key: self.printit(key))
            Button(self, text=key, command=func).pack(side=TOP, fill=BOTH)
        Quitter(self).pack(side=TOP, fill=BOTH)

    def printit(self, name):
        print(name, 'returns =>', demos[name]())    # fetch, call, print

if __name__ == '__main__': Demo().mainloop()

Quitter只是一个 class 的退出按钮。

我的问题是如何重写此代码以使用可调用的 class object ( __call__ ) 而不是lambda来推迟对实际处理程序的调用？

Answer 1

好吧，在这种情况下，您可以执行以下操作：

from tkinter import *
from dialogTable import demos       # button callback handlers
from quitter import Quitter         # attach a quit object to me

class Wrapper:
    def __init__(self, func, key):
        self.func = func
        self.key = key
    def __call__(self):
        return self.func(self.key)

class Demo(Frame):
    def __init__(self, parent=None, **options):
        Frame.__init__(self, parent)
        self.pack()
        Label(self, text="Basic demos").pack()
        for key in demos:
            func = Wrapper(self.printit, key)
            Button(self, text=key, command=func).pack(side=TOP, fill=BOTH)
        Quitter(self).pack(side=TOP, fill=BOTH)

    def printit(self, name):
        print(name, 'returns =>', demos[name]())    # fetch, call, print

if __name__ == '__main__': Demo().mainloop()