Useful snippets

Indexing streams

Here are a few builtin recipes for indexing streams/sequences.

But don't forget to checkout creek.tools.dynamically_index

with count indices

from functools import partial
from operator import itemgetter

annotator = partial(enumerate)
deannotator = partial(map, itemgetter(1))

assert list(annotator('abc')) == [(0, 'a'), (1, 'b'), (2, 'c')]
assert list(deannotator([(0, 'a'), (1, 'b'), (2, 'c')])) == ['a', 'b', 'c']
# But list is not the right iterator aggregator for this; ''.join is.
''.join(deannotator([(0, 'a'), (1, 'b'), (2, 'c')])) == 'abc'

with time

import time

def add_time(x):
    return time.time(), x

annotator = partial(map, add_time)
deannotator = partial(map, itemgetter(1))  # same as the index counter
list(annotator('abc'))
# [(1637094309.799298, 'a'), (1637094309.799298, 'b'), (1637094309.799298, 'c')]
assert ''.join(deannotator(annotator('abc'))) == 'abc'