Alex Martelli <aleaxit at yahoo.com> writes:
> Lists are mutable, which makes "creating bound methods" (or the equivalent
> thereof) absolutely unavoidable -- e.g.:
> xxx = somelist.somemethod
> " alter somelist at will "
> yyy = xxx( <args if needed> )
>
> xxx needs to be able to refer back to somelist at call time, clearly.
It depends on the source code. In your example, I agree it is
unavoidable. In the much more common case of
yyy = somelist.somemethod(<args if needed>)
one could call the code of somemethod without creating a bound method,
and, in some cases, without creating the argument tuple. It would be
good if, for
>>> def x(a):
... a.append(1)
...
the code could change from
2 0 LOAD_FAST 0 (a)
3 LOAD_ATTR 1 (append)
6 LOAD_CONST 1 (1)
9 CALL_FUNCTION 1
12 POP_TOP
13 LOAD_CONST 0 (None)
16 RETURN_VALUE
to
2 0 LOAD_FAST 0 (a)
3 LOAD_CONST 2 (append)
6 LOAD_CONST 1 (1)
9 CALL_METHOD 1
12 POP_TOP
13 LOAD_CONST 0 (None)
16 RETURN_VALUE
where CALL_METHOD would read the method name from
stack. Unfortunately, that would be a semantical change, a __getattr__
would not be called anymore. Perhaps that can be changed to
2 0 LOAD_FAST 0 (a)
3 LOAD_METHOD 1 (append)
6 LOAD_CONST 1 (1)
9 CALL_METHOD 1
12 POP_TOP
13 LOAD_CONST 0 (None)
16 RETURN_VALUE
where LOAD_METHOD has the option of returning an fast_method object
(which exists only once per type type and method), and CALL_METHOD
would check for whether there is a fast_method object on stack, and
then explicitly pop "self" from the stack as well.
> Few situations are as favourable as this one -- immutable object, no
> arguments, just two possible constant-returning callables needed.
Most cases are as favourable as this one. If you immediately call the
bound method, and then discard the bound-method-object, there is no
point in creating it first. The exception is the getattr-style
computation of callables, where getattr cannot know that the result is
going to be called right away.
Regards,
Martin
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