What exactly are bound methods?

[Erik Max Francis]

Kylotan wrote:
> 
> Although I see lots of references to them in various documentation, I
> can't find a decent explanation of exactly what they are. I'm guessing
> that it's a reference to a method that remembers which object it came
> from, and that when it's called, it passes that object as the first
> parameter (which would conventionally be 'self'). Is this correct?

Yep:

>>> class C:
...  def f(self, x):
...   print x
... 
>>> c = C() # c is an instance of C
>>> C
<class __main__.C at 0x402e141c>
>>> C.f # the unbound method
<unbound method C.f>
>>> c.f # the bound method
<bound method C.f of <__main__.C instance at 0x402e4c8c>>
>>> C.f(c, 1) # invoking unbound methods requires passing the instance
1
>>> c.f(1) # bound methods already contain the instance
1


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