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Re: PyWart: os.path needs immediate attention!

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On 7/29/2011 8:50 PM, Steven D'Aprano wrote:

> Guido has a rule of thumb: "No constant arguments". Or another way to put
> it: if a function takes an argument which is nearly always a constant
> (usually, but not always, a flag) then it is usually better off as two
> functions.

I do not really understand his 'rule'*. The stdlib has lots of functions 
with boolean flags and params which default to None and are seldom 
over-ridden.

* Which is to say, it feels more like his gut feeling applied on a 
case-by-case basis than an actual rule that anyone could apply in any 
objective manner.

> Especially if the implementation looks like this:
>
> def get_thing(argument, flag):
>      if flag:
>          return one_thing(argument)
>      else:
>          return another_thing(argument)

If the rule is limited to this situation, where no code is shared, it 
seems pretty sensible.

> Argument flags which do nothing but change the behaviour of the function
> from Mode 1 to Mode 2 are an attractive nuisance: they seem like a good
> idea, but aren't. Consider it a strong guideline rather than a law, but
> it's one I would think very long and hard about before violating.
>
> But having said that, I'm currently writing a library where nearly all the
> functions violate the No Constant Argument rule. (The API isn't yet stable,
> so I may still change my mind.) Make of that what you will.

See * above ;-).

Terry Jan Reedy

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PyWart: os.path needs immediate attention! rantingrick <rantingrick@gmail.com> - 2011-07-29 10:22 -0700
  Re: PyWart: os.path needs immediate attention! Andrew Berg <bahamutzero8825@gmail.com> - 2011-07-29 12:53 -0500
    Re: PyWart: os.path needs immediate attention! harrismh777 <harmar@member.fsf.org> - 2011-07-29 14:41 -0500
      Re: PyWart: os.path needs immediate attention! "Waldek M." <wm@localhost.localdomain> - 2011-07-29 21:55 +0200
    Re: PyWart: os.path needs immediate attention! Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-30 10:50 +1000
      Function "modes" vs. separate functions (was: PyWart: os.path needs immediate attention!) Andrew Berg <bahamutzero8825@gmail.com> - 2011-07-29 20:15 -0500
        Re: Function "modes" vs. separate functions Ben Finney <ben+python@benfinney.id.au> - 2011-07-30 11:57 +1000
          Re: Function "modes" vs. separate functions Andrew Berg <bahamutzero8825@gmail.com> - 2011-07-29 21:28 -0500
      Re: PyWart: os.path needs immediate attention! Terry Reedy <tjreedy@udel.edu> - 2011-07-30 09:48 -0400
      Re: PyWart: os.path needs immediate attention! Robert Kern <robert.kern@gmail.com> - 2011-07-30 23:31 -0400
  Re: PyWart: os.path needs immediate attention! Teemu Likonen <tlikonen@iki.fi> - 2011-07-29 23:07 +0300
    Re: PyWart: os.path needs immediate attention! Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-30 10:57 +1000
      Re: PyWart: os.path needs immediate attention! Teemu Likonen <tlikonen@iki.fi> - 2011-08-01 11:19 +0300
        Re: PyWart: os.path needs immediate attention! rantingrick <rantingrick@gmail.com> - 2011-08-02 09:03 -0700
          Re: PyWart: os.path needs immediate attention! Chris Angelico <rosuav@gmail.com> - 2011-08-02 17:36 +0100
  Re: PyWart: os.path needs immediate attention! Chris Angelico <rosuav@gmail.com> - 2011-07-30 06:25 +1000
  Re: PyWart: os.path needs immediate attention! Corey Richardson <kb1pkl@aim.com> - 2011-07-29 16:44 -0400
  Re: PyWart: os.path needs immediate attention! Alister Ware <alister.ware@ntlworld.com> - 2011-07-29 21:21 +0000
    Re: PyWart: os.path needs immediate attention! Andrew Berg <bahamutzero8825@gmail.com> - 2011-07-29 16:36 -0500
  Re: PyWart: os.path needs immediate attention! Chris Angelico <rosuav@gmail.com> - 2011-07-30 07:43 +1000
  Re: PyWart: os.path needs immediate attention! Terry Reedy <tjreedy@udel.edu> - 2011-07-29 19:30 -0400
  Re: PyWart: os.path needs immediate attention! Michael Poeltl <michael.poeltl@univie.ac.at> - 2011-07-30 02:30 +0200
    Re: PyWart: os.path needs immediate attention! Grant Edwards <invalid@invalid.invalid> - 2011-07-30 15:33 +0000
      Re: PyWart: os.path needs immediate attention! Andrew Berg <bahamutzero8825@gmail.com> - 2011-07-30 10:56 -0500
        Re: PyWart: os.path needs immediate attention! alex23 <wuwei23@gmail.com> - 2011-08-02 23:52 -0700
  Re: PyWart: os.path needs immediate attention! Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-07-29 22:17 -0700
  Re: PyWart: os.path needs immediate attention! Gelonida N <gelonida@gmail.com> - 2011-08-03 11:52 +0200

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