Re: enum question

[Terry Hancock]

On Friday 04 March 2005 02:54 pm, M.N.A.Smadi wrote:
> does python support a C-like enum statement where one can define a 
> variable with prespesified range of values?

No, but in most situations where I would've used an enum, I use a 
trivial class like this:

class states:
ON, OFF, UNKNOWN, UNDEFINED, INCOMPREHENSIBLE, SILLY = range(6)

The values are actually integers of course.  Then I can pass named values to a 
function:

from silly import walk, states

walk(kind=states.SILLY)

If you want to make them more like a bitfield, you could always do this instead:

class properties:
AUDIBLE, VISIBLE, SPEAKABLE = [2**i for i in range(3)]

then you can have, e.g.:

evil(allowed=False, AUDIBLE|VISIBLE|SPEAKABLE)

if mode & AUDIBLE: hear()
if mode & VISIBLE: see()

etc.

Obviously if you want more rigid assurance of the behavior of the variable
in question you'd need more work. But most of the time, enums are just to
make the code more readable, so I do this, which is extremely compact,
and yet pretty clear.  You *can* drop the enum values into the module
namespace, but then importing them is a pain, so I like to qualify them
with the class as shown.

Cheers,
Terry


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Re: enum question

[Carl Banks]

M.N.A.Smadi wrote:
> does python support a C-like enum statement where one can define a
> variable with prespesified range of values?

The thing is, variables don't have types; objects do.  A variable can
be bound to an object of any type, so there's no way to prespecify a
range of values for a variable.

Your question has the air of someone who's evaluating Python features,
considering whether to try it.  If so, you might need to widen your
worldview a little to understand Python; its variables are
fundamentally different from C, and things like enums don't make much
sense in Python because of it.  However, Python is versatile enough
that you can get something to that effect if you really need it.


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Re: enum question

[Patrick Useldinger]

M.N.A.Smadi wrote:
does python support a C-like enum statement where one can define a 
variable with prespesified range of values?

thanks
m.smadi
>>> BLUE, RED, GREEN = 1,5,8
>>> BLUE
1
>>> RED
5
>>> GREEN
8
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Re: enum question

[Stephen Toledo-Brown]

M.N.A.Smadi wrote:
does python support a C-like enum statement where one can define a 
variable with prespesified range of values?
Not built in, but there are various solutions available, some simpler 
than others. See the Infrequently Asked Questions: 
http://www.norvig.com/python-iaq.html

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Re: enum question

[Larry Bates]

Not completely sure I understand (my C is weak).
But you can do:

x=range(9)

x's contents will be
[0,1,2,3,4,5,6,7,8]

or

x=range(12,25)

x's conetnst will be
[12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]

if you mean a way to limit x's contents to a predefined
list of values, you need to write a class for that and
override the __setattr__ method to limit.  Quick
example:

class a:
def __setattr__(self, attr, x):
if x in range(10): self.__dict__[attr]=x
else:
print "error, x not in ", str(range(10))

>>> x=a()
>>> x.value=11
error, x not in  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> x.value=8
>>>

Larry Bates


M.N.A.Smadi wrote:
> does python support a C-like enum statement where one can define a
> variable with prespesified range of values?
> 
> thanks
> m.smadi
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enum question

[M.N.A.Smadi]

does python support a C-like enum statement where one can define a 
variable with prespesified range of values?

thanks
m.smadi
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