Map two lists into a dictionary in Python

Question

Imagine that you have:

keys = ('name', 'age', 'food')
values = ('Monty', 42, 'spam')

What is the simplest way to produce the following dictionary ?

dict = {'name' : 'Monty', 'age' : 42, 'food' : 'spam'}

This code works, but I'm not really proud of it :

dict = {}
junk = map(lambda k, v: dict.update({k: v}), keys, values)

Answer 1

Like this:

>>> keys = ['a', 'b', 'c']
>>> values = [1, 2, 3]
>>> dictionary = dict(zip(keys, values))
>>> print dictionary
{'a': 1, 'b': 2, 'c': 3}

Voila :-) The pairwise dict constructor and zip function are awesomely useful: http://www.python.org/doc/2.5.2/lib/built-in-funcs.html#dict

Answer 2

>>> keys = ('name', 'age', 'food')
>>> values = ('Monty', 42, 'spam')
>>> dict(zip(keys, values))
{'food': 'spam', 'age': 42, 'name': 'Monty'}

Answer 3

Try this:

>>> import itertools
>>> keys = ('name', 'age', 'food')
>>> values = ('Monty', 42, 'spam')
>>> adict = dict(itertools.izip(keys,values))
>>> adict
{'food': 'spam', 'age': 42, 'name': 'Monty'}

It was the simplest solution I could come up with.

--Mike Davis

PS It's also more economical in memory consumption compared to zip.

Answer 4

If you need to transform keys or values before creating a dictionary then a generator expression could be used. Example:

>>> adict = dict((str(k), v) for k, v in zip(['a', 1, 'b'], [2, 'c', 3]))

Take a look Code Like a Pythonista: Idiomatic Python.