Add powerset to list_utils; improve chord parser.

1 files changed, 18 insertions, 1 deletions

diff --git a/list_utils.py b/list_utils.py
index 5c70df3..1141af2 100644
--- a/list_utils.py
+++ b/list_utils.py
@@ -6,7 +6,7 @@
 
 import random
 from collections import Counter
-from itertools import islice
+from itertools import chain, combinations, islice
 from typing import Any, Iterator, List, MutableSequence, Sequence, Tuple
 
 
@@ -307,6 +307,23 @@ def _binary_search(lst: Sequence[Any], target: Any, low: int, high: int) -> Tupl
         return (False, low)
 
 
+def powerset(lst: Sequence[Any]) -> Iterator[Sequence[Any]]:
+    """Returns the powerset of the items in the input sequence.
+
+    >>> for x in powerset([1, 2, 3]):
+    ...     print(x)
+    ()
+    (1,)
+    (2,)
+    (3,)
+    (1, 2)
+    (1, 3)
+    (2, 3)
+    (1, 2, 3)
+    """
+    return chain.from_iterable(combinations(lst, r) for r in range(len(lst) + 1))
+
+
 if __name__ == '__main__':
     import doctest