Map list onto dictionary

Question

Is there a way to map a list onto a dictionary? What I want to do is give it a function that will return the name of a key, and the value will be the original value. For example

Answer 1

>>> dict((a[0], a) for a in "hello world".split())
{'h': 'hello', 'w': 'world'}

If you want to use a function instead of subscripting, use operator.itemgetter:

>>> from operator import itemgetter
>>> first = itemgetter(0)
>>> dict((first(x), x) for x in "hello world".split())
{'h': 'hello', 'w': 'world'}

Or as a function:

>>> dpair = lambda x : (first(x), x)
>>> dict(dpair(x) for x in "hello world".split())
{'h': 'hello', 'w': 'world'}

Finally, if you want more than one word per letter as a possibility, use collections.defaultdict

>>> from collections import defaultdict
>>> words = defaultdict(set)
>>> addword = lambda x : words[first(x)].add(x)
>>> for word in "hello house home hum world wry wraught".split():
        addword(word)


>>> print words['h']
set(['house', 'hello', 'hum', 'home'])