[Tutor] enumeration in C++

[Erik Price]

On Tuesday, April 2, 2002, at 01:05  PM, Jeff Shannon wrote:

> As you can see, this lets us get the weeday corresponding to a specific 
> number, or
> the number for a particular weekday name, and it lets us do a certain 
> amount of
> arithmetic with weekdays (if we're careful).  One caution with the 
> arithmetic --
> we *do* want to be sure that the result of all of our arithmetic is 
> within the
> range of the length of our list (0-6).  We can use the modulus 
> operator ( % ) to
> do this:
>
>>>> weekdays[ weekdays.index('friday') + 5 ]
> Traceback (most recent call last):
>   File "<interactive input>", line 1, in ?
> IndexError: list index out of range
>>>> weekdays[ (weekdays.index('friday') + 5) % len(weekdays) ]
> 'wednesday'
>>>> weekdays.index('friday') + 5
> 10
>>>> (weekdays.index('friday') + 5) % len(weekdays)
> 3
>>>>
>
> Hope this makes some sense to you.  :)

It made a lot of sense to me AND it showed me a good reason to use the 
modulus operator.  (I'm not saying good reasons don't exist, I just 
haven't seen many of them yet.)

Now I know what enumerations are used for, and why they don't exist in 
Python (and how to wing it if I really want to use them, though I would 
probably use a tuple since it seems that enumerations don't change*).


Erik

* ... but then, when I tried the code, it says that tuples don't have 
the attribute 'index' -- what gives? I thought that tuples and lists 
were pretty much the same, except for immutableness on the part of 
tuples.