In Python, is there a way to bind an unbound method without calling it?
I am writing a wxPython program, and for a certain class I decided it'd be nice to group the data of all of my buttons together as a class-level list of tuples, like so:
class MyWidget(wx.Window):
buttons = [("OK", OnOK),
("Cancel", OnCancel)]
# ...
def Setup(self):
for text, handler in MyWidget.buttons:
# This following line is the problem line.
b = wx.Button(parent, label=text).Bind(wx.EVT_BUTTON, handler)
The problem is, since all of the values of handler
are unbound methods, my program explodes in a spectacular blaze and I weep.
I was looking around online for a solution to what seems like should be a relatively straightforward, solvable problem. Unfortunately I couldn't find anything. Right now, I'm using functools.partial
to work around this, but does anyone know if there's a clean-feeling, healthy, Pythonic way to bind an unbound method to an instance and continue passing it around without calling it?
All functions are also descriptors, so you can bind them by calling their __get__
method:
bound_handler = handler.__get__(self, MyWidget)
Here's R. Hettinger's excellent guide to descriptors.
As a self-contained example pulled from Keith's comment:
def bind(instance, func, as_name=None):
"""
Bind the function *func* to *instance*, with either provided name *as_name*
or the existing name of *func*. The provided *func* should accept the
instance as the first argument, i.e. "self".
"""
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
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