Question

Consider the following dictionary, d:

d = {'a': 3, 'b': 2, 'c': 3, 'd': 4, 'e': 5}

I want to return the first N key:value pairs from d (N <= 4 in this case). What is the most efficient method of doing this?

Answer 1

Prior to Python 3.6 there is no such thing a the "first n" keys because a dict doesn’t remember which keys were inserted first.

You can get first n iteration sorted key-value pairs though:

n_items = take(n, d.items())

This uses the implementation of take from the itertools recipes:

from itertools import islice

def take(n, iterable):
    """Return the first n items of the iterable as a list."""
    return list(islice(iterable, n))

See it working online: ideone

For Python < 3.6

n_items = take(n, d.iteritems())