[Tutor] constants, flags or whatever

[Steve Willoughby]

Dave Kuhlman wrote:
> On Wed, Dec 19, 2007 at 09:41:13PM -0500, bob gailer wrote:
> 
>> 1 - I see no value in introducing variables. I'd just use string constants:
>>
>> action = "moving"
>> .
>> .
>> if action == "jumping":
>>
>> etc.
> 
> I agree.  But, some people do prefer something that looks a bit
> like an enum.  If so, here is a Python idiom for enums:

One big advantage to using variables over string constants is that
there is a big danger of misspelling one of the constants and not
noticing the error.

action = "moving"
...
if action == "moveing":
   # oops, this never gets executed


if you had used variables, Python would catch the error as an
attempt to use an undefined variable:

action = MOVING
...
if action == MOVEING:  <-- error caught by python


> Mode_none, Mode_moving, Mode_inserting, Mode_jumping = range(4)
> 
> action = Mode_moving
> 
> if action == Mode_jumping:
>     o
>     o
>     o
> 
> - Dave
> 
>