On Thu, 28 Jan 2010 17:01:38 +0100, Roald de Vries wrote:
> Question out of general interest in the language: If I would want to
> generate such functions in a for-loop, what would I have to do? This
> doesn't work:
>
> class Move(object):
> def __call__(self, direction):
> return direction
>
> move = Move()
>
> for f in ['up', 'down', 'right', 'left']:
> move.__dict__[f] = lambda: move(f)
>
> ... because now 'move.up()' returns 'left' because thats the current
> value of f. Is there a way to 'expand' f in the loop? Or a reason that
> you never should use this?
Possibly the simplest way is to use Python's handling of default values
to get the result you want:
for f in ['up', 'down', 'right', 'left']:
move.__dict__[f] = lambda f=f: move(f)
BTW, there's no need to explicitly reference move.__dict__:
for f in ['up', 'down', 'right', 'left']:
setattr(move, f, lambda f=f: move(f))
--
Steven
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