"""Utility functions for working with iterators and collections."""
import itertools
def partition(pred, iterable):
"""Use a predicate to partition entries into false entries and true entries."""
# https://stackoverflow.com/questions/8793772/how-to-split-a-sequence-according-to-a-predicate
# NOTE: this might iterate over the collection twice
# NOTE: need to use filter(s) here because we're lazily dealing with iterators
it1, it2 = itertools.tee(iterable)
return itertools.filterfalse(pred, it1), filter(pred, it2) # pylint: disable=bad-builtin
def first_occurrences(iterable):
"""Return list where subsequent occurrences of repeat elements have been removed."""
added = set()
result = []
for elt in iterable:
if elt not in added:
result.append(elt)
added.add(elt)
return result
