In python, we have beautiful unpacking:
a, b, c = [1,2,3]
and even
a, b, *c = [1,2,3,4,5]
We also have dictionary destructing for purposes of keywords:
myfunc(**mydict)
You can currently unpack a dictionary, but its almost certainly not what
you would intend.
a, b, c = {'a': 1, 'c': 3, 'b': 2}.values()
In python 3.6+ this is better since the dictionary is insertion-ordered,
but is still not really what one would probably want.
It would be cool to have a syntax that would unpack the dictionary to
values based on the names of the variables. Something perhaps like:
a, b, c = **mydict
which would assign the values of the keys 'a', 'b', 'c' to the variables.
The problem with this approach is that it only works if the key is also a
valid variable name. Another syntax could potentially be used to specify
the keys you care about (and the order). Perhaps:
a, b, c = **mydict('a', 'b', 'c')
I dont really like that syntax, but it gives a good idea.
One way to possibly achieve this today without adding syntax support could
be simply adding a builtin method to the dict class:
a, b, c = mydict.unpack('a', 'b', 'c')
The real goal of this is to easily get multiple values from a dictionary.
The current ways of doing this are:
a, b, c, = mydict['a'], mydict['b'], mydict['c']
or
a = mydict['a']
b = mydict['b']
c = mydict['c']
The later seams to be more common. Both are overly verbose in my mind.
One thing to consider however is the getitem vs get behavior. mydict['a']
would raise a KeyError if 'a' wasnt in the dict, whereas mydict.get('a')
would return a "default" (None if not specified). Which behavior is chosen?
Maybe there is no clean solutions, but those are my thoughts. Anyone have
feedback/ideas on this?
Nick
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