bpo-35498: Added slice support to PathLib parents attribute. (GH-11165)

Added slice support to the `pathlib.Path.parents` sequence. For a `Path` `p`, slices of `p.parents` should return the same thing as slices of `tuple(p.parents)`.

Doc/library/pathlib.rst

@@ -336,6 +336,8 @@ Pure paths provide the following methods and properties:
       >>> p.parents[2]
       PureWindowsPath('c:/')
 
+   .. versionchanged:: 3.10
+      Slice support was added.
 
 .. data:: PurePath.parent
 

Doc/whatsnew/3.10.rst

@@ -244,6 +244,12 @@ descriptors without copying between kernel address space and user
 address space, where one of the file descriptors must refer to a
 pipe. (Contributed by Pablo Galindo in :issue:`41625`.)
 
+pathlib
+-------
+
+Added slice support to :meth:`~pathlib.Path.parents`.
+(Contributed by Joshua Cannon in :issue:`35498`)
+
 py_compile
 ----------
 

Lib/pathlib.py

@@ -630,6 +630,8 @@ class _PathParents(Sequence):
             return len(self._parts)
 
     def __getitem__(self, idx):
+        if isinstance(idx, slice):
+            return tuple(self[i] for i in range(*idx.indices(len(self))))
         if idx < 0 or idx >= len(self):
             raise IndexError(idx)
         return self._pathcls._from_parsed_parts(self._drv, self._root,

Lib/test/test_pathlib.py

@@ -440,6 +440,12 @@ class _BasePurePathTest(object):
         self.assertEqual(par[0], P('a/b'))
         self.assertEqual(par[1], P('a'))
         self.assertEqual(par[2], P('.'))
+        self.assertEqual(par[0:1], (P('a/b'),))
+        self.assertEqual(par[:2], (P('a/b'), P('a')))
+        self.assertEqual(par[:-1], (P('a/b'), P('a')))
+        self.assertEqual(par[1:], (P('a'), P('.')))
+        self.assertEqual(par[::2], (P('a/b'), P('.')))
+        self.assertEqual(par[::-1], (P('.'), P('a'), P('a/b')))
         self.assertEqual(list(par), [P('a/b'), P('a'), P('.')])
         with self.assertRaises(IndexError):
             par[-1]
@@ -454,6 +460,12 @@ class _BasePurePathTest(object):
         self.assertEqual(par[0], P('/a/b'))
         self.assertEqual(par[1], P('/a'))
         self.assertEqual(par[2], P('/'))
+        self.assertEqual(par[0:1], (P('/a/b'),))
+        self.assertEqual(par[:2], (P('/a/b'), P('/a')))
+        self.assertEqual(par[:-1], (P('/a/b'), P('/a')))
+        self.assertEqual(par[1:], (P('/a'), P('/')))
+        self.assertEqual(par[::2], (P('/a/b'), P('/')))
+        self.assertEqual(par[::-1], (P('/'), P('/a'), P('/a/b')))
         self.assertEqual(list(par), [P('/a/b'), P('/a'), P('/')])
         with self.assertRaises(IndexError):
             par[3]
@@ -905,6 +917,12 @@ class PureWindowsPathTest(_BasePurePathTest, unittest.TestCase):
         self.assertEqual(len(par), 2)
         self.assertEqual(par[0], P('z:a'))
         self.assertEqual(par[1], P('z:'))
+        self.assertEqual(par[0:1], (P('z:a'),))
+        self.assertEqual(par[:-1], (P('z:a'),))
+        self.assertEqual(par[:2], (P('z:a'), P('z:')))
+        self.assertEqual(par[1:], (P('z:'),))
+        self.assertEqual(par[::2], (P('z:a'),))
+        self.assertEqual(par[::-1], (P('z:'), P('z:a')))
         self.assertEqual(list(par), [P('z:a'), P('z:')])
         with self.assertRaises(IndexError):
             par[2]
@@ -913,6 +931,12 @@ class PureWindowsPathTest(_BasePurePathTest, unittest.TestCase):
         self.assertEqual(len(par), 2)
         self.assertEqual(par[0], P('z:/a'))
         self.assertEqual(par[1], P('z:/'))
+        self.assertEqual(par[0:1], (P('z:/a'),))
+        self.assertEqual(par[0:-1], (P('z:/a'),))
+        self.assertEqual(par[:2], (P('z:/a'), P('z:/')))
+        self.assertEqual(par[1:], (P('z:/'),))
+        self.assertEqual(par[::2], (P('z:/a'),))
+        self.assertEqual(par[::-1], (P('z:/'), P('z:/a'),))
         self.assertEqual(list(par), [P('z:/a'), P('z:/')])
         with self.assertRaises(IndexError):
             par[2]
@@ -921,6 +945,12 @@ class PureWindowsPathTest(_BasePurePathTest, unittest.TestCase):
         self.assertEqual(len(par), 2)
         self.assertEqual(par[0], P('//a/b/c'))
         self.assertEqual(par[1], P('//a/b'))
+        self.assertEqual(par[0:1], (P('//a/b/c'),))
+        self.assertEqual(par[0:-1], (P('//a/b/c'),))
+        self.assertEqual(par[:2], (P('//a/b/c'), P('//a/b')))
+        self.assertEqual(par[1:], (P('//a/b'),))
+        self.assertEqual(par[::2], (P('//a/b/c'),))
+        self.assertEqual(par[::-1], (P('//a/b'), P('//a/b/c')))
         self.assertEqual(list(par), [P('//a/b/c'), P('//a/b')])
         with self.assertRaises(IndexError):
             par[2]

Misc/ACKS

@@ -270,6 +270,7 @@ Daniel Calvelo
 Tony Campbell
 Giovanni Cappellotto
 Brett Cannon
+Joshua Cannon
 Tristan Carel
 Mike Carlton
 Pierre Carrier

Misc/NEWS.d/next/Library/2018-12-14-13-29-17.bpo-35498.LEJHl7.rst

@@ -0,0 +1 @@
+Add slice support to :meth:`~pathlib.Path.parents`.