Re: Is this unpythonic?

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From	"Frank Millman" <frank@chagford.com>
Subject	Re: Is this unpythonic?
Date	Fri, 8 May 2015 12:53:19 +0200
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"Steven D'Aprano" <steve+comp.lang.python@pearwood.info> wrote in message 
news:554c8b0a$0$12992$c3e8da3$5496439d@news.astraweb.com...
> On Fri, 8 May 2015 06:01 pm, Frank Millman wrote:
>
>> Hi all
>>
[...]
>>
>> However, every time I look at my own code, and I see   "def x(y, z=[]):
>> ....."   it looks wrong because I have been conditioned to think of it as
>> a gotcha.
>
> It is a gotcha, and a code smell.
>
> http://www.joelonsoftware.com/articles/Wrong.html
>

Interesting read - thanks.

> You can use it, but with care: code smells aren't necessarily wrong, they
> just need to be looked at a little more carefully.
>
>
>> Would it be more pythonic to change them all to use the alternative
>> "z=None", or is it ok to leave it as it is? Or to phrase it differently,
>> how would an experienced pythonista react on seeing this when reviewing 
>> my
>> code?
>
> I would change it to z=None *unless* you actually required the list to be
> mutated, e.g. if you were using it as a cache.
>

Ok, you and Joel have convinced me. I will change it to z=None.

> Does z have to be a list? Could you use an empty tuple instead?
>
> def x(y, z=()): ...
>

That was Chris' suggestion as well (thanks Chris).

The idea appealed to me, but then I found a situation where I pass in a 
dictionary instead of a list, so that would not work.

Replacing them all with None is cleaner and, I now agree, more pythonic.

Thanks for the good advice.

Frank

Thread

Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-08 10:01 +0200
  Re: Is this unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-08 20:08 +1000
    Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-08 12:53 +0200
      Re: Is this unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-09 01:07 +1000
        Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-09 07:56 +0200
        Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-09 08:51 +0200
          Re: Is this unpythonic? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-09 19:47 +1200
            Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-09 11:10 +0200
    Re: Is this unpythonic? Dave Angel <davea@davea.name> - 2015-05-08 08:04 -0400
      Re: Is this unpythonic? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-05-10 10:04 +0200
        Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-10 10:58 +0200
          Re: Is this unpythonic? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2015-05-10 11:54 +0200
            Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-10 12:40 +0200
    Re: Is this unpythonic? "Frank Millman" <frank@chagford.com> - 2015-05-08 15:12 +0200

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