How to Bind Unbound Methods in Python Without Invoking Them?

Unbinding the Gordian Knot: Binding Unbound Methods Seamlessly

In Python, binding unbound methods without invoking them can present a coding challenge. Consider this scenario:

<code class="python">class MyWidget(wx.Window):
    buttons = [("OK", OnOK), ("Cancel", OnCancel)]

    def setup(self):
        for text, handler in MyWidget.buttons:
            b = wx.Button(parent, label=text).bind(wx.EVT_BUTTON, handler)</code>

Here, handler represents an unbound method, leading to runtime errors. While functools.partial offers a workaround, Python's innate descriptor capabilities provide an elegant solution.

Unveiling the Power of Descriptors

All functions in Python possess intrinsic descriptor properties. By leveraging their __get__ method, unbound methods can be bound to an instance:

<code class="python">bound_handler = handler.__get__(self, MyWidget)</code>

This technique enables binding of unbound methods without triggering their execution.

A Comprehensive Example

To illustrate, let's implement a custom bind function:

<code class="python">def bind(instance, func, as_name=None):
    if as_name is None:
        as_name = func.__name__
    bound_method = func.__get__(instance, instance.__class__)
    setattr(instance, as_name, bound_method)
    return bound_method</code>

Utilizing this bind function, we can achieve the desired functionality:

<code class="python">class Thing:
    def __init__(self, val):
        self.val = val

something = Thing(21)

def double(self):
    return 2 * self.val

bind(something, double)
something.double()  # returns 42</code>

By embracing the power of descriptors, we effortlessly bind unbound methods, unlocking a myriad of coding possibilities without compromising on Pythonic principles.

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