Implemented not found behavior

Added custom exception to track negative search results.
Updated prefix bisect functions with raise NotFound.
Updated find all function.

Author: shorodilov

src/bisearch/prefix.py

@@ -1,6 +1,10 @@
 from typing import List
 
 
+class NotFound(Exception):
+    """Raised in case the search function failed to find requested value"""
+
+
 def bisect_right(origin: List[str], search: str = "") -> int:
     """Return the most right index
 
@@ -12,6 +16,8 @@ def bisect_right(origin: List[str], search: str = "") -> int:
     :return: the index of the first string starting with search prefix
     :rtype: int
 
+    :raise: NotFound
+
     """
 
     low: int = 0
@@ -27,6 +33,9 @@ def bisect_right(origin: List[str], search: str = "") -> int:
         else:
             high = idx
 
+    if low >= len(origin) and not origin[-1].startswith(search):
+        raise NotFound(f"'{search}'")
+
     return low
 
 
@@ -41,6 +50,8 @@ def bisect_left(origin: List[str], search: str = "") -> int:
     :return: the index after the last string starting with search prefix
     :rtype: int
 
+    :raise: NotFound
+
     """
 
     low: int = 0
@@ -56,11 +67,29 @@ def bisect_left(origin: List[str], search: str = "") -> int:
         else:
             high = idx
 
+    if low >= len(origin):
+        raise NotFound(f"'{search}'")
+
     return low
 
 
 def find_all(origin: List[str], search: str = "") -> List[str]:
-    start = bisect_left(origin, search)
-    end = bisect_right(origin, search)
+    """Return strings starting with prefix
+
+    :param origin: the list of strings
+    :type origin: list[str]
+    :param search: the prefix to search, defaults to empty string
+    :type search: str
+
+    :return: the list of strings starting with the search prefix
+    :rtype: list[str]
+    """
+
+    try:
+        start = bisect_left(origin, search)
+        end = bisect_right(origin, search)
+
+        return origin[start:end]
 
-    return origin[start:end]
+    except NotFound:
+        return []

tests/bisearch/test_prefix.py

@@ -1,4 +1,7 @@
+import pytest
+
 from bisearch import prefix
+from bisearch.prefix import NotFound
 
 
 def test_prefix_right(strings_fixtures, pr_fixture):
@@ -28,5 +31,15 @@ def test_find_all_default(strings_small):
     assert prefix.find_all(strings_small) == strings_small
 
 
+def test_prefix_right_negative(strings_small):
+    with pytest.raises(NotFound):
+        prefix.bisect_right(strings_small, "d")
+
+
+def test_prefix_left_negative(strings_small):
+    with pytest.raises(NotFound):
+        prefix.bisect_left(strings_small, "d")
+
+
 def test_find_all_negative(strings_small):
     assert prefix.find_all(strings_small, "d") == []