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 :)

Why not use an actual argument parser that supports default values properly? — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented Nov 22, 2013 at 0:35
I just started doing it actually. But want to keep the constants at the top too, to make things easier. — xcorat
– xcorat, Commented Nov 22, 2013 at 1:07

Amadan · Accepted Answer · 2013-11-22 00:40:20Z

3

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.

answered Nov 22, 2013 at 0:40

Amadan

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1 Comment

xcorat Over a year ago

kool. I was now thinking the same, but didn't occur that i could put DEFAULT before. I didn't want to have PADDR and paddr :)

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