[Python-ideas] Is there any idea about dictionary destructing?

[Nikolas Vanderhoof]

Although that particular example once compiled to python will generate many
many lines of code:

​

On Sat, Apr 7, 2018 at 4:17 PM, Nikolas Vanderhoof <
nikolasrvanderhoof at gmail.com> wrote:

> And this should print:
>
> 'some data'
> 1
> 2
> 3
>
> On Sat, Apr 7, 2018 at 4:16 PM, Nikolas Vanderhoof <
> nikolasrvanderhoof at gmail.com> wrote:
>
>> This would be a very handy feature, but Coconut (which is just python
>> with some extra functional-style features) also has support for this kind
>> of pattern-matching:
>> http://coconut-lang.org
>>
>>
>> ​Since Coconut will compile to Python (2 or 3) you can just write in
>> Coconut and use the resulting code in your Python.
>>
>> Using your first example in coconut would be nearly identical, except I
>> believe the entire dictionary must be specified (I am not sure about this).
>>
>> data = {
>>     'direct': 'some data',
>>     'nested': {
>>         'lst_data': [1, 2, 3],
>>         'int_data': 1
>>     }
>> }
>>
>> {
>>     'direct': direct,
>>     'nested': {
>>         'lst_data': [a, b, c],
>>         'int_data': _
>>     }
>> } = data
>>
>> print(direct)
>> print(a)
>> print(b)
>> print(c)
>>
>>
>> And this should print:
>>
>> On Sat, Apr 7, 2018 at 1:26 PM, thautwarm <yaoxiansamma at gmail.com> wrote:
>>
>>> We know that Python support the destructing of iterable objects.
>>>
>>> m_iter = (_ for _ in range(10))
>>> a, *b, c = m_iter
>>>
>>> That's pretty cool! It's really convenient when there're many corner
>>> cases to handle with iterable collections.
>>> However destructing in Python could be more convenient if we support
>>> dictionary destructing.
>>>
>>> In my opinion, dictionary destructing is not difficult to implement and
>>> makes the syntax more expressive. A typical example is data access on
>>> nested data structures(just like JSON), destructing a dictionary makes
>>> the logic quite clear:
>>>
>>> data = {
>>>     "direct": "some data",
>>>     "nested": {
>>>         "lst_data": [1, 2, 3],
>>>         "int_data": 1
>>>     }
>>> }
>>> {
>>>    "direct": direct,
>>>     "nested": {
>>>         "lst_data": [a, b, c],
>>>     }
>>> } = data
>>>
>>>
>>> Dictionary destructing might not be very well-known but it really helps.
>>> The operations on nested key-value collections are very frequent, and the
>>> codes for business logic are not readable enough until now. Moreover Python
>>> is now popular in data processing which must be enhanced by the entire
>>> support of data destructing.
>>>
>>> Here are some implementations of other languages:
>>> Elixir, which is also a popular dynamic language nowadays.
>>>
>>> iex> %{} = %{:a => 1, 2 => :b}
>>> %{2 => :b, :a => 1}
>>> iex> %{:a => a} = %{:a => 1, 2 => :b}
>>> %{2 => :b, :a => 1}
>>> iex> a
>>> 1
>>> iex> %{:c => c} = %{:a => 1, 2 => :b}
>>> ** (MatchError) no match of right hand side value: %{2 => :b, :a => 1}
>>>
>>> And in F#, there is something similar to dictionary
>>> destructing(actually, this destructs `struct` instead)
>>> type MyRecord = { Name: string; ID: int } let IsMatchByName record1
>>> (name: string) = match record1 with | { MyRecord.Name = nameFound;
>>> MyRecord.ID = _; } when nameFound = name -> true | _ -> false let
>>> recordX = { Name = "Parker"; ID = 10 } let isMatched1 = IsMatchByName
>>> recordX "Parker" let isMatched2 = IsMatchByName recordX "Hartono"
>>>
>>> All of them partially destructs(or matches) a dictionary.
>>>
>>> thautwarm
>>>
>>>
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>>>
>>>
>>
>
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