On Jan 22, 2010, at 1:06 PM, Martin Drautzburg wrote:
On 22 Jan., 11:56, Roald de Vries <r...@roalddevries.nl> wrote:
Hi Martin,
On Jan 21, 2010, at 8:43 AM, Martin Drautzburg 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?
You could do something like this:
class Move(object):
def __call__(self, direction):
print(direction)
return 0
def up(self):
return self('up')
move = Move()
Now move.up() means move('up'), and you can obviously do similar
things for other directions.- Zitierten Text ausblenden -
- Zitierten Text anzeigen -
I had thought about that too. It gets a bit tricky when there is more
than one parameter and it completely fails whan a parameter can REALLY
be a number or an arbitrary string. Think: move(direction, distance)
For extra parameters:
class Move(object):
def __call__(self, direction, param1, param2, *params, **dict):
print(direction)
return 0
def up(self, *params, **dict):
return self('up', *params, **dict)
move = Move()
On Jan 22, 2010, at 1:06 PM, Martin Drautzburg wrote:
On 22 Jan., 11:56, Roald de Vries <r...@roalddevries.nl> wrote:
Hi Martin,
On Jan 21, 2010, at 8:43 AM, Martin Drautzburg 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?
You could do something like this:
class Move(object):
def __call__(self, direction):
print(direction)
return 0
def up(self):
return self('up')
move = Move()
Now move.up() means move('up'), and you can obviously do similar
things for other directions.- Zitierten Text ausblenden -
- Zitierten Text anzeigen -
I had thought about that too. It gets a bit tricky when there is more
than one parameter
For extra parameters:
class Move(object):
def __call__(self, direction, param1, param2, *params, **dict):
print(direction)
return 0
def up(self, *params, **dict):
return self('up', *params, **dict)
move = Move()
and it completely fails whan a parameter can REALLY
be a number or an arbitrary string. Think: move(direction, distance)
For a number, move.up(10) wouldn't be too bad. For an arbitrary
string, you always have __getattr__ and __getattribute__. But if you
like this style of coding, you should probably switch to Ruby.
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