Is there any function can unpack any sequence in Python?

Question

a = types.SimpleNamespace()
b = dict()
[a.__setattr__(key, value) for key, value in b]

Now I would like to use map: list(map(a.setattr, b.items())), but the item of b.items() is a tuple, not key and value. I know the Python has the unpack syntax, so I am curious is there any function can unpack sequence too so that I can use it in map.

Why would you use a simple namespace rather than `a = {k:v for k,v in b.items()}`? — OneCricketeer, Oct 11 '18 at 07:08
Should you clarify that you do *not* want to use `lambda` within the map? If not, why is having a tuple an issue? — OneCricketeer, Oct 11 '18 at 07:10
[**Don't use comprehensions for side effects!**](https://stackoverflow.com/questions/5753597/is-it-pythonic-to-use-list-comprehensions-for-just-side-effects) Use a normal loop instead. — Aran-Fey, Oct 11 '18 at 07:26
@cricket_007 because you can access members with `.` syntax rather than string lookups. — Peter Wood, Oct 11 '18 at 07:35
@cricket_007 Ok, lambda is a function too, altough it must be defined by the user. — acgtyrant, Oct 11 '18 at 07:40

score 0 · Answer 1 · answered Oct 11 '18 at 07:12

You can use itertools.starmap:

In [46]: list(itertools.starmap(a.__setattr__, {'a': '1', 'b': '2'}.items()))
Out[46]: [None, None]

In [47]: a
Out[47]: namespace(a='1', b='2')

Though I do not think that list comprenehsion or list(map is more readable than a simple loop here.

blhsing · Answer 2 · 2018-10-11T07:20:54.227

0

You can use itertools.starmap to map the sequence of key-value pairs to a.setattr:

list(starmap(a.__setattr__, b.items()))

edited Oct 11 '18 at 07:20

answered Oct 11 '18 at 07:12

blhsing

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Why `map(tuple, b.items())`? – awesoon Oct 11 '18 at 07:13
Indeed. Fixed then. Thanks. – blhsing Oct 11 '18 at 07:15

Is there any function can unpack any sequence in Python?

2 Answers2