X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=list_utils.py;h=91af8f9eb924fb7e7e04932d58a1bcb6eded0690;hb=e8fbbb7306430478dec55d2c963eed116d8330cc;hp=b877e381041d32564789232e1bb7329cc04503e6;hpb=444d1e5f3e9a39759079736302e3404018141b02;p=python_utils.git

diff --git a/list_utils.py b/list_utils.py
index b877e38..91af8f9 100644
--- a/list_utils.py
+++ b/list_utils.py
@@ -1,8 +1,10 @@
 #!/usr/bin/env python3
 
+"""Some useful(?) utilities for dealing with Lists."""
+
 from collections import Counter
 from itertools import islice
-from typing import Any, Iterator, List, Mapping, Sequence, Tuple
+from typing import Any, Iterator, List, Sequence, Tuple
 
 
 def shard(lst: List[Any], size: int) -> Iterator[Any]:
@@ -65,7 +67,7 @@ def remove_list_if_one_element(lst: List[Any]) -> Any:
         return lst
 
 
-def population_counts(lst: List[Any]) -> Mapping[Any, int]:
+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
@@ -200,9 +202,9 @@ def ngrams(lst: Sequence[Any], n):
         yield lst[i : i + n]
 
 
-def permute(seq: Sequence[Any]):
+def permute(seq: str):
     """
-    Returns all permutations of a sequence; takes O(N^2) time.
+    Returns all permutations of a sequence; takes O(N!) time.
 
     >>> for x in permute('cat'):
     ...     print(x)
@@ -217,11 +219,12 @@ def permute(seq: Sequence[Any]):
     yield from _permute(seq, "")
 
 
-def _permute(seq: Sequence[Any], path):
-    if len(seq) == 0:
+def _permute(seq: str, path: str):
+    seq_len = len(seq)
+    if seq_len == 0:
         yield path
 
-    for i in range(len(seq)):
+    for i in range(seq_len):
         car = seq[i]
         left = seq[0:i]
         right = seq[i + 1 :]
@@ -264,9 +267,7 @@ def binary_search(lst: Sequence[Any], target: Any, *, sanity_check=False) -> Tup
     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: