Importing variables non-deterministic?

[Chris Angelico]

On Mon, Aug 19, 2013 at 9:16 AM, Antoon Pardon
<antoon.pardon at rece.vub.ac.be> wrote:
> Op 19-08-13 09:45, Dave Angel schreef:
>> Antoon Pardon wrote:
>>> I think you are overstating your case. Classes and functions are
>>> variables too and in general nobody seems to have a problem with them
>>> being global.
>>>
>>
>> It's global *variables* that are to be avoided.  constants like clsases
>> and functions are fine.  On the other hand, class attributes can be
>> variable, and thus are to be avoided when reasonable.
>
> Python has no constants. Classes and functions can be changed just like
> any other variable. I agree that classes and function are generally
> meant to be constant, but often enought so are global int variables.

# telnet.py
IAC = 0xFF
GA = 0xF9
WILL = 0xFB
WONT = 0xFC
DO = 0xFD
DONT = 0xFE


# connection.py
from telnet import IAC,DO,DONT


To be sure, Python won't stop me from changing the value of DONT. But
it's a constant, and its value is defined elsewhere (RFC 854). (In
this instance, an enum would probably be the better option; but this
is an example of a more general case.)

In connection.py, I don't care that I've taken a "copy" of the integer
0xFE. It's never going to change; it is a constant in the best
tradition of "named number". I could hard-code 0xFE everywhere and the
code would work *just fine*, but it'd be less readable, so I don't.

Python does have constants. It just doesn't have interpreter support
for them. Same as private members, in fact.

ChrisA