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Re: recursive function: use a global or pass a parameter?

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On Sat, Jan 17, 2015 at 4:49 AM, Tim <jtim.arnold@gmail.com> wrote:
> I want to get a union of all the values that any 'things' key may have, even in a nested dictionary (and I do not know beforehand how deep the nesting might go):
>
> d = {'things':1, 'two':{'things':2}}
>
> def walk(obj, res):
>     if not hasattr(obj, 'keys'):
>         return set(), set()
>
>     if 'things' in obj:
>         res.add(obj['things'])
>
>     for k in obj:
>         walk(obj[k], res)
>
>     return res
>
> walk(d, set()) # returns {1, 2}
>
> Is it better to use a global to keep track of the values or does it even matter?

I would use a parameter rather than a global, but I'd make the
parameter optional:

def all_keys(obj, accum=None):
    if accum is None: accum=set()
    if 'things' in obj:
        res.add(obj['things'])
    for val in obj.values():
        all_keys(val, accum)
    return all_keys

ChrisA

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recursive function: use a global or pass a parameter? Tim <jtim.arnold@gmail.com> - 2015-01-16 09:49 -0800
  Re: recursive function: use a global or pass a parameter? Chris Angelico <rosuav@gmail.com> - 2015-01-17 04:56 +1100
    Re: recursive function: use a global or pass a parameter? Rustom Mody <rustompmody@gmail.com> - 2015-01-16 10:22 -0800
  Re: recursive function: use a global or pass a parameter? Peter Otten <__peter__@web.de> - 2015-01-16 19:34 +0100
    Re: recursive function: use a global or pass a parameter? Tim <jtim.arnold@gmail.com> - 2015-01-16 10:48 -0800
    Re: recursive function: use a global or pass a parameter? Yawar Amin <yawar.amin@gmail.com> - 2015-01-16 18:23 -0800
      Re: recursive function: use a global or pass a parameter? Yawar Amin <yawar.amin@gmail.com> - 2015-01-16 21:29 -0800
      Re: recursive function: use a global or pass a parameter? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-18 10:25 +1300
  Re: recursive function: use a global or pass a parameter? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 11:20 +1300
    Re: recursive function: use a global or pass a parameter? Chris Angelico <rosuav@gmail.com> - 2015-01-17 10:49 +1100
  Re: recursive function: use a global or pass a parameter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 21:15 +1100
    Re: recursive function: use a global or pass a parameter? Roy Smith <roy@panix.com> - 2015-01-17 10:20 -0500
      Re: recursive function: use a global or pass a parameter? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-18 10:07 +1300
  Re: recursive function: use a global or pass a parameter? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-17 17:30 +0000
    Re: recursive function: use a global or pass a parameter? Chris Angelico <rosuav@gmail.com> - 2015-01-18 06:27 +1100

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