dn <pythonl...@danceswithmice.info> writes:
> On 31/03/2021 01.22, Loris Bennett wrote:
>> Jon Ribbens <jon+use...@unequivocal.eu> writes:
>>> On 2021-03-30, Loris Bennett <loris.benn...@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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