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Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!)

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On 2014-02-13 04:11, Steven D'Aprano wrote:
> give_me_an_even_number()
> => returns 42
> give_me_an_even_number()
> => returns 23
> 
> Hmmm. There's a bug in give_me_an_even_number(). How do I reproduce
> that bug? What arguments do I pass? Oh, the same no-arguments as
> for the working call.
> 
> Clearly, the function must have *hidden state*. Hidden state (e.g.
> a global variable) makes it hard to reason about the function call,
> since you don't know what the hidden state is. So that's also a bit
> smelly.

I'd even go so far as to claim that this is the primary reason a
zero-argument function is a code-smell.  Not because zero-argument
functions smell, but because hidden-state smells and zero-argument
functions imply hidden-state.  Date/time functions are a personal pet
peeve for just this reason, and require addressing the hidden-state
of the system clock regardless of parameter-count.  Thus instead of
something like

  class Person:
    def __init__(self, name, dob):
      self.name = name
      self.dob = dob
    def age(self):
      return datetime.date.today() - self.dob

I do

  def age(self, as_of=None):
    if as_of is None:
      as_of = datetime.date.today()
    return as_of = self.dob

allowing me to test the function with known dates.

> > There are code smells that are the opposite in fact, methods with
> > long parameter lists are generally seen as code smell (“passing a
> > paragraph”).
> 
> Absolutely! You'll get no disagreement from me there.

*coughtkintercough*

-tkc

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PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Rick Johnson <rantingrickjohnson@gmail.com> - 2014-02-10 10:45 -0800
  Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-02-10 19:15 +0000
  Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Ned Batchelder <ned@nedbatchelder.com> - 2014-02-10 14:17 -0500
  Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Rotwang <sg552@hotmail.co.uk> - 2014-02-10 21:12 +0000
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Ned Batchelder <ned@nedbatchelder.com> - 2014-02-10 17:00 -0500
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Terry Reedy <tjreedy@udel.edu> - 2014-02-10 17:59 -0500
  Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Chris Angelico <rosuav@gmail.com> - 2014-02-11 09:30 +1100
  Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Steven D'Aprano <steve@pearwood.info> - 2014-02-11 06:30 +0000
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Tim Chase <python.list@tim.thechases.com> - 2014-02-11 09:26 -0600
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Travis Griggs <travisgriggs@gmail.com> - 2014-02-11 07:36 -0800
      Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-02-11 18:07 +0200
        Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Chris Angelico <rosuav@gmail.com> - 2014-02-12 03:14 +1100
      Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Steven D'Aprano <steve@pearwood.info> - 2014-02-13 04:11 +0000
        Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Chris Angelico <rosuav@gmail.com> - 2014-02-13 15:30 +1100
          Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Roy Smith <roy@panix.com> - 2014-02-13 09:58 -0500
            Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Chris Angelico <rosuav@gmail.com> - 2014-02-14 06:17 +1100
        Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Tim Chase <python.list@tim.thechases.com> - 2014-02-13 05:39 -0600
        Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Tim Chase <python.list@tim.thechases.com> - 2014-02-13 05:51 -0600
        Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-13 15:00 -0700
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Chris Angelico <rosuav@gmail.com> - 2014-02-12 02:52 +1100
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Travis Griggs <travisgriggs@gmail.com> - 2014-02-11 08:19 -0800
    Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!) Terry Reedy <tjreedy@udel.edu> - 2014-02-11 12:57 -0500

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