CODEWITHSUNDEEP
python
Doo Dah
Doo Dah

Reputation: 4029

Python list of tuples to dictionary

In Python 2.7, suppose I have a list with 2 member sets like this

d = [(1, 'value1'), (2, 'value2'), (3, 'value3')]

What is the easiest way in python to turn it into a dictionary like this:

d = {1 : 'value1', 2 : 'value2', 3 : 'value3'}

Or, the opposite, like this?

d = {'value1' : 1, 'value2': 2, 'value3' : 3}

Thanks

Upvotes: 2

Views: 364

Answers (6)

jamylak
jamylak

Reputation: 133514

>>> d = [(1, 'value1'), (2, 'value2'), (3, 'value3')]
>>> dict(d)
{1: 'value1', 2: 'value2', 3: 'value3'}
>>> dict(map(reversed, d))
{'value3': 3, 'value2': 2, 'value1': 1}

Upvotes: 0

cmh
cmh

Reputation: 10927

If your list is in the form of a list of tuples then you can simply use dict().

In [5]: dict([(1, 'value1'), (2, 'value2'), (3, 'value3')])
Out[5]: {1: 'value1', 2: 'value2', 3: 'value3'}

A dictionary comprehension can be used to construct the reversed dictionary:

In [13]: { v : k for (k,v) in [(1, 'value1'), (2, 'value2'), (3, 'value3')] }
Out[13]: {'value1': 1, 'value2': 2, 'value3': 3}

Upvotes: 4

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250891

>>> lis = [(1, 'value1'), (2, 'value2'), (3, 'value3')]

Use dict() for the first one:

>>> dict(lis)
{1: 'value1', 2: 'value2', 3: 'value3'}

And a dict comprehension for the second one:

>>> {v:k for k,v in lis}
{'value3': 3, 'value2': 2, 'value1': 1}

dict() converts an iterable into a dict:

>>> print dict.__doc__
dict() -> new empty dictionary
dict(mapping) -> new dictionary initialized from a mapping object's
    (key, value) pairs
dict(iterable) -> new dictionary initialized as if via:
    d = {}
    for k, v in iterable:
        d[k] = v
dict(**kwargs) -> new dictionary initialized with the name=value pairs
    in the keyword argument list.  For example:  dict(one=1, two=2)

Upvotes: 3

freakish
freakish

Reputation: 56467

lst = [(1, 'value1'), (2, 'value2'), (3, 'value3')]

To turn it to dict, just do

dict(lst)

to reverse it, you can do

dict((b,a) for a,b in lst)

Upvotes: 2

Hank Gay
Hank Gay

Reputation: 71939

dict(my_list) should probably do the trick. Also, I think you have a list of tuples, not sets.

Upvotes: 1

John La Rooy
John La Rooy

Reputation: 304137

The dict constructor can take a sequence. so...

dict([(1, 'value1'), (2, 'value2'), (3, 'value3')])

and the reverse is best done with a dictionary comprehension

{k: v for v,k in [(1, 'value1'), (2, 'value2'), (3, 'value3')]}

Upvotes: 7

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