Easier and more self documenting patterns for loading/saving Persistent

[python_utils.git] / list_utils.py

diff --git a/list_utils.py b/list_utils.py
index 71630dc9a6fdb4d968f890b2ac4d3b8cb78360d2..8f92be30c45fba8531654895f7a03da29b18dae7 100644 (file)
--- a/list_utils.py
+++ b/list_utils.py
@@ -1,8 +1,13 @@
 #!/usr/bin/env python3
 
+# © Copyright 2021-2022, Scott Gasch
+
+"""Some useful(?) utilities for dealing with Lists."""
+
+import random
 from collections import Counter
-from itertools import islice
-from typing import Any, Iterator, List, Mapping, Sequence, Tuple
+from itertools import chain, combinations, islice
+from typing import Any, Iterator, List, MutableSequence, Sequence, Tuple
 
 
 def shard(lst: List[Any], size: int) -> Iterator[Any]:
@@ -65,7 +70,7 @@ def remove_list_if_one_element(lst: List[Any]) -> Any:
         return lst
 
 
-def population_counts(lst: List[Any]) -> Counter:
+def population_counts(lst: Sequence[Any]) -> Counter:
     """
     Return a population count mapping for the list (i.e. the keys are
     list items and the values are the number of occurrances of that
@@ -230,9 +235,31 @@ def _permute(seq: str, path: str):
         yield from _permute(cdr, path + car)
 
 
-def binary_search(
-    lst: Sequence[Any], target: Any, *, sanity_check=False
-) -> Tuple[bool, int]:
+def shuffle(seq: MutableSequence[Any]) -> MutableSequence[Any]:
+    """Shuffles a sequence into a random order.
+
+    >>> random.seed(22)
+    >>> shuffle([1, 2, 3, 4, 5])
+    [3, 4, 1, 5, 2]
+
+    >>> shuffle('example')
+    'empaelx'
+
+    """
+    if isinstance(seq, str):
+        import string_utils
+
+        return string_utils.shuffle(seq)
+    else:
+        random.shuffle(seq)
+        return seq
+
+
+def scramble(seq: MutableSequence[Any]) -> MutableSequence[Any]:
+    return shuffle(seq)
+
+
+def binary_search(lst: Sequence[Any], target: Any) -> Tuple[bool, int]:
     """Performs a binary search on lst (which must already be sorted).
     Returns a Tuple composed of a bool which indicates whether the
     target was found and an int which indicates the index closest to
@@ -258,7 +285,7 @@ def binary_search(
     AssertionError
 
     """
-    if sanity_check:
+    if __debug__:
         last = None
         for x in lst:
             if last is not None:
@@ -267,9 +294,7 @@ def binary_search(
     return _binary_search(lst, target, 0, len(lst) - 1)
 
 
-def _binary_search(
-    lst: Sequence[Any], target: Any, low: int, high: int
-) -> Tuple[bool, int]:
+def _binary_search(lst: Sequence[Any], target: Any, low: int, high: int) -> Tuple[bool, int]:
     if high >= low:
         mid = (high + low) // 2
         if lst[mid] == target:
@@ -282,6 +307,23 @@ def _binary_search(
         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