Code style query: multiple assignments in if/elif tree

Date	2014-04-01 01:33 +1100
Subject	Code style query: multiple assignments in if/elif tree
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.8744.1396276875.18130.python-list@python.org> (permalink)

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Call this a code review request, if you like. I'm wondering how you'd
go about coding something like this.

Imagine you're in a train, and the brakes don't apply instantly. The
definition, in the interests of passenger comfort, is that the first
second of brake application has an acceleration of 0.2 m/s/s, the next
second has 0.425 m/s/s, and thereafter full effect of 0.85 m/s/s. You
have a state variable that says whether the brakes have just been
applied, have already been applied for at least two seconds, or
haven't yet been applied at all. Problem: Work out how far you'll go
before the brakes reach full power, and how fast you'll be going at
that point.

Here's how I currently have the code. The variable names are a tad
long, as this was also part of me teaching my brother Python.

# Already got the brakes fully on
if mode=="Brake2": distance_to_full_braking_power, speed_full_brake =
0.0, curspeed
# The brakes went on one second ago, they're nearly full
elif mode=="Brake1": distance_to_full_braking_power, speed_full_brake
= curspeed - 0.2125, curspeed - 0.425
# Brakes aren't on.
else: distance_to_full_braking_power, speed_full_brake = (curspeed -
0.1) + (curspeed - 0.4125), curspeed - 0.625
# If we hit the brakes now (or already have hit them), we'll go
another d meters and be going at s m/s before reaching full braking
power.

But I don't like the layout. I could change it to a single assignment
with expression-if, but that feels awkward too. How would you lay this
out?

(Note that the "else" case could have any of several modes in it, so I
can't so easily use a dict.)

ChrisA

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Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 01:33 +1100
  Re: Code style query: multiple assignments in if/elif tree Marko Rauhamaa <marko@pacujo.net> - 2014-03-31 18:40 +0300
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 03:03 +1100
      Re: Code style query: multiple assignments in if/elif tree Rustom Mody <rustompmody@gmail.com> - 2014-03-31 09:20 -0700
        Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 03:29 +1100
          Re: Code style query: multiple assignments in if/elif tree "Rhodri James" <rhodri@wildebst.org.uk> - 2014-03-31 21:31 +0100
    Re: Code style query: multiple assignments in if/elif tree Ned Batchelder <ned@nedbatchelder.com> - 2014-03-31 17:42 -0400
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 09:50 +1100
    Re: Code style query: multiple assignments in if/elif tree Ben Finney <ben+python@benfinney.id.au> - 2014-04-01 09:57 +1100
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 10:12 +1100
      Re: Code style query: multiple assignments in if/elif tree Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-01 00:57 +0000
    Re: Code style query: multiple assignments in if/elif tree Ethan Furman <ethan@stoneleaf.us> - 2014-03-31 17:30 -0700
  Re: Code style query: multiple assignments in if/elif tree Steven D'Aprano <steve@pearwood.info> - 2014-04-01 04:26 +0000
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 16:01 +1100
      Re: Code style query: multiple assignments in if/elif tree Steven D'Aprano <steve@pearwood.info> - 2014-04-01 07:20 +0000
        Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 18:35 +1100
          Re: Code style query: multiple assignments in if/elif tree Steven D'Aprano <steve@pearwood.info> - 2014-04-01 08:07 +0000
            Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 19:12 +1100
        Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 02:18 -0600
        Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 02:24 -0600
    Re: Code style query: multiple assignments in if/elif tree Rustom Mody <rustompmody@gmail.com> - 2014-03-31 22:45 -0700
      Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 02:05 -0400
      Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 00:28 -0600
    Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 00:13 -0600
    Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 02:24 -0400
    Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 00:39 -0600
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 17:55 +1100
      Re: Code style query: multiple assignments in if/elif tree Steven D'Aprano <steve@pearwood.info> - 2014-04-01 07:29 +0000
        Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 18:49 +1100
        Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 02:29 -0600
        Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 19:56 +1100
    Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 03:21 -0400
    Re: Code style query: multiple assignments in if/elif tree Chris Angelico <rosuav@gmail.com> - 2014-04-01 18:26 +1100
    Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 03:34 -0400
    Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 03:39 -0400
    Re: Code style query: multiple assignments in if/elif tree David Hutto <dwightdhutto@gmail.com> - 2014-04-01 03:46 -0400
    Re: Code style query: multiple assignments in if/elif tree Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-01 02:55 -0600

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