https://github.com/python/cpython/commit/bd73e72b4a9f019be514954b1d40e64dc3a...

commit: bd73e72b4a9f019be514954b1d40e64dc3a5e81c branch: master author: Allen W. Smith, Ph.D committer: Antoine Pitrou date: 2017-08-30T00:52:18+02:00 summary:

... @@ -307,6 +309,10 @@ def imap(self, func, iterable, chunksize=1): )) return result else: + if chunksize < 1: + raise ValueError( + "Chunksize must be 1+, not {0:n}".format( + chunksize)) assert chunksize > 1

It looks like removing this assert statement was missed. --Chris

task_batches = Pool._get_tasks(func, iterable, chunksize) result = IMapIterator(self._cache) @@ -334,7 +340,9 @@ def imap_unordered(self, func, iterable, chunksize=1): )) return result else: - assert chunksize > 1 + if chunksize < 1: + raise ValueError( + "Chunksize must be 1+, not {0!r}".format(chunksize)) task_batches = Pool._get_tasks(func, iterable, chunksize) result = IMapUnorderedIterator(self._cache) self._taskqueue.put(