python 'constants' and changing them

Question

Hi this is more of a style question. I have a small script that works with a socket, and I have constants (i know they are not real constants, but heyy, at least they are in capital) that declare some properties,

# Port address for the serial port to read the weight from
PADDR = '/dev/ttyUSB0'
# socket address uri, backlog, and buffer
SADDR = 'localhost:28000'
BACKLG = 0
BUFF = 1024
# for cross platform compatibility use epoch in unix time
EPOCH_START = datetime(1970, 1, 1)

I however might add functionality to change these by parsing arguments. So the question is, should I just change these directly when parsing arguments?

or should I be nice and use the above constants as defaults and change the options which I would then pass around to functions who need them? This seems a bit too much, but then again, I don't want to write code that will be frowned upon :)

Answer 1

Have DEFAULT_PADDR as a constant; but paddr as a variable with DEFAULT_PADDR as its default value. Do not change a "constant", even if it is just a matter of style - your code becomes cryptic.

I.e. for now, do this:

DEFAULT_PADDR = '/dev/ttyUSB0'
# ...
paddr = DEFAULT_PADDR

then you can change paddr when you add argument parsing.