til/python/iterate-first-n-items-from-enumerable.md

Iterate First N Items From Enumerable

As I'm working through the 2nd chapter of Build a Large Language Model (from scratch), I came across a code example processing a dictionary of words. This example used a for loop to print out each dictionary entry until an index of 50 was reached on then it did a break.

This struck me as an odd way to grab and process N items from a list. I did some searching and found itertools which provides islice.

from itertools import islice

# preprocess words from a file into a word list
all_words = ... # not shown here

vocab = {token: integer for integer, token in enumerate(all_words)}
for item in islice(enumerate(vocab.items()), 50):
    print(item)

The islice function is a better approach because the intention (to grab the first 50 things) is encoded in the function call rather than buried in a loop body. It also has equivalent memory efficiency to the original example because it lazily processes the list of vocab items.