CODEWITHSUNDEEP
pythondictionaryunpack
user2624744
user2624744

Reputation: 773

Unpack dictionary without knowledge of its key name

If I have some dictionary like:

d = {'keyname': ['foo', 'bar']}

and I don't know the key name how I would unpack this dict in two variables?

This doesn't work:

k,v = d

I could iterate over this dict like:

for k, v in d.items():
    # k and v are now available

But I think this is not the "pythonic" way enough

How can I do this without using a for-loop?

"d" can always have only ONE key:val pair.

Upvotes: 0

Views: 123

Answers (3)

hariK
hariK

Reputation: 3059

d = {'keyname': ['foo', 'bar']}

for k in d.keys(): key = k

val = d[k]

print key, val

Upvotes: 0

Tanveer Alam
Tanveer Alam

Reputation: 5275

In Python 2.x If your dictionary is always going to be of length 1 then this can be one possible solution:

>>> d = {'keyname': ['foo', 'bar']}
>>> k, v = d.keys()[0], d.values()[0]
>>> k
'keyname'
>>> v
['foo', 'bar']

For both Python 2.x and 3.x Using .items()

>>> k, v = d.items()[0]
>>> k
'keyname'
>>> v
['foo', 'bar']

For python 3.x

>>> d = {'keyname': ['foo', 'bar']}
>>> k, v = tuple(d.keys())[0], tuple(d.values())[0]
>>> k
'keyname'
>>> v
['foo', 'bar']

Upvotes: 2

user2555451
user2555451

Reputation:

You can use iterable unpacking:

>>> d = {'keyname': ['foo', 'bar']}
>>> [(k, v)] = d.items()
>>> k
'keyname'
>>> v
['foo', 'bar']
>>>

This works in both Python 2.x and Python 3.x.

Note however that if you are using Python 2.x, it would be slightly more efficient to use d.iteritems() instead of d.items():

>>> from timeit import timeit
>>> d = {'keyname': ['foo', 'bar']}
>>> timeit('[(k, v)] = d.items()', 'from __main__ import d')
0.786108849029695
>>> timeit('[(k, v)] = d.iteritems()', 'from __main__ import d')
0.6730112346680928
>>>

This is because iteritems returns an iterator while items builds an unnecessary list.

Upvotes: 3

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