Canonical conversion of dict of dicts to list of dicts

[Loris Bennett]

dn <PythonList at DancesWithMice.info> writes:

> On 31/03/2021 01.22, Loris Bennett wrote:
>> Jon Ribbens <jon+usenet at unequivocal.eu> writes:
>>> On 2021-03-30, Loris Bennett <loris.bennett at fu-berlin.de> wrote:
>>>> If I have dict of dicts, say
>>>>
>>>>   dod = {
>>>>       "alice":
>>>>       {
>>>>           "lang": "python",
>>>>           "level": "expert"
>>>>       },
>>>>       "bob":
>>>>       {
>>>>           "lang": "perl",
>>>>           "level": "noob"
>>>>       }
>>>>   }
>>>>
>>>> is there a canonical, or more pythonic, way of converting the outer key
>>>> to a value to get a list of dicts, e.g
> ...
>
>>>>
>>>> than just
>>>>
>>>>   lod = []
>>>>   for name in dod:
>>>>       d = dod[name]
>>>>       d["name"] = name
>>>>       lod.append(d)
>
>
> Please be aware of the 'law of unintended consequences' - what
> functional programmers call "side-effects"!
>
> At the end of the above code, not only has "lod" been created (per spec)
> but "dod" is no longer what it once was.
>
> Thus, future code may not rely upon the (above) structure. Of course, if
> by "convert" you mean transform, ie that "dod" will be del()[eted]
> afterwards, such may be completely unimportant.
>
>
> from pprint import pprint as pp
> import copy
>
> dod = {
>       "alice":
>       {
>           "lang": "python",
>           "level": "expert"
>       },
>       "bob":
>       {
>           "lang": "perl",
>           "level": "noob"
>       }
> }
>
> original = copy.deepcopy( dod )
> lod = []
> for name in dod:
>     d = dod[name]
>     d["name"] = name
>     lod.append(d)
>
> print( original == dod )
> pp(dod)
> pp(original)
>
>
> False
> {'alice': {'lang': 'python', 'level': 'expert', 'name': 'alice'},
>  'bob': {'lang': 'perl', 'level': 'noob', 'name': 'bob'}}
> {'alice': {'lang': 'python', 'level': 'expert'},
>  'bob': {'lang': 'perl', 'level': 'noob'}}

Thanks for pointing that out.  Coming from Perl that's something I need
to watch out for.  So if I do

  $ a = ["alice", "bob", "carol"]
  $ b = a
  $ b[1] = "bert"
  $ b
  ['alice', 'bert', 'carol']
  $ a
  ['alice', 'bert', 'carol']

I see that changing one list changes the other because 'a' and 'b' are
just bindings to the same object.  However, If I look at non-list
variables:

   $ a = "bob"
   $ b = a
   $ b = "bert"
   $ a
  'bob'

that doesn't happen.  What's the rational for that and where can I find
it in the Python documentation?

Cheers,

Loris

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