Slicing a dictionary

Question

I have a dictionary, and would like to pass a part of it to a function, that part being given by a list (or tuple) of keys. Like so:

# the dictionary d = {1:2, 3:4, 5:6, 7:8}  # the subset of keys I'm interested in l = (1,5) 

Now, ideally I'd like to be able to do this:

>>> d[l] {1:2, 5:6} 

... but that's not working, since it will look for a key named (1,5). And d[1,5] isn't even valid Python (though it seems it would be handy).

I know I can do this:

>>> dict([(key, value) for key,value in d.iteritems() if key in l]) {1: 2, 5: 6} 

or this:

>>> dict([(key, d[key]) for key in l]) 

which is more compact ... but I feel there must be a "better" way of doing this. Am I missing a more elegant solution?

(I'm using Python 2.7)

Answer 1

On Python 3 you can use the itertools islice to slice the dict.items() iterator

import itertools  d = {1: 2, 3: 4, 5: 6}  dict(itertools.islice(d.items(), 2))  {1: 2, 3: 4} 

Note: this solution does not take into account specific keys. It slices by internal ordering of d, which in Python 3.7+ is guaranteed to be insertion-ordered.