Merge pull request #606 from more-itertools/subslices

Add subslices recipe
more-itertools · Apr 19, 2022 · 59aeef1 · 59aeef1
2 parents d971c86 + 74bc878
commit 59aeef1
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diff --git a/more_itertools/recipes.py b/more_itertools/recipes.py
@@ -52,6 +52,7 @@
     'repeatfunc',
     'roundrobin',
     'sliding_window',
+    'subslices',
     'tabulate',
     'tail',
     'take',
@@ -767,3 +768,17 @@ def sliding_window(iterable, n):
     for x in it:
         window.append(x)
         yield tuple(window)
+
+
+def subslices(iterable):
+    """Return all contiguous non-empty subslices of *iterable*.
+
+        >>> list(subslices('ABC'))
+        [['A'], ['A', 'B'], ['A', 'B', 'C'], ['B'], ['B', 'C'], ['C']]
+
+    This is similar to :func:`substrings`, but emits items in a different
+    order.
+    """
+    seq = list(iterable)
+    slices = starmap(slice, combinations(range(len(seq) + 1), 2))
+    return map(operator.getitem, repeat(seq), slices)
diff --git a/more_itertools/recipes.pyi b/more_itertools/recipes.pyi
@@ -108,3 +108,4 @@ def triplewise(iterable: Iterable[_T]) -> Iterator[Tuple[_T, _T, _T]]: ...
 def sliding_window(
     iterable: Iterable[_T], n: int
 ) -> Iterator[Tuple[_T, ...]]: ...
+def subslices(iterable: Iterable[_T]) -> Iterator[List[_T]]: ...
diff --git a/tests/test_recipes.py b/tests/test_recipes.py
@@ -806,3 +806,32 @@ def test_basic(self):
             with self.subTest(expected=expected):
                 actual = list(mi.sliding_window(iterable, n))
                 self.assertEqual(actual, expected)
+
+
+class SubslicesTests(TestCase):
+    def test_basic(self):
+        for iterable, expected in [
+            ([], []),
+            ([1], [[1]]),
+            ([1, 2], [[1], [1, 2], [2]]),
+            (iter([1, 2]), [[1], [1, 2], [2]]),
+            ([2, 1], [[2], [2, 1], [1]]),
+            (
+                'ABCD',
+                [
+                    ['A'],
+                    ['A', 'B'],
+                    ['A', 'B', 'C'],
+                    ['A', 'B', 'C', 'D'],
+                    ['B'],
+                    ['B', 'C'],
+                    ['B', 'C', 'D'],
+                    ['C'],
+                    ['C', 'D'],
+                    ['D'],
+                ],
+            ),
+        ]:
+            with self.subTest(expected=expected):
+                actual = list(mi.subslices(iterable))
+                self.assertEqual(actual, expected)