On Thu, Jan 21, 2010 at 8:43 AM, Martin Drautzburg <martin.drautzb...@web.de> wrote: > Hello all, > > When passing parameters to a function, you sometimes need a paramter > which can only assume certain values, e.g. > > def move (direction): > ... > If direction can only be "up", "down", "left" or "right", you can solve > this by passing strings, but this is not quite to the point: > > - you could pass invalid strings easily > - you need to quote thigs, which is a nuisance > - the parameter IS REALLY NOT A STRING, but a direction > > Alternatively you could export such symbols, so when you "import *" you > have them available in the caller's namespace. But that forces you > to "import *" which pollutes your namespace. > > What I am really looking for is a way > > - to be able to call move(up) > - having the "up" symbol only in the context of the function call > > So it should look something like this > > ... magic, magic ... > move(up) > ... unmagic, unmagic ... > print up > > This should complain that "up" is not defined during the "print" call, > but not when move() is called. And of course there should be as little > magic as possible. > > Any way to achieve this?
It probably can be done, but in my opinion even it can, it would be ugly. I would just define "up" as some global constant - I don't see why it would be a problem that it's defined when you don't need it. In fact, I think it would be beneficial - you can then have direction-valued variables, so that you can (for example) implement "go the same direction I went last time". If that kind of thing happens more often, it might be useful to have a Direction class, to be able to easily program in things like "the opposite of up is down" and "right from right is back". -- André Engels, andreeng...@gmail.com -- http://mail.python.org/mailman/listinfo/python-list
