gh-107089: Improve Shelf.clear method performance

Lib/shelve.py

@@ -226,6 +226,13 @@ def __init__(self, filename, flag='c', protocol=None, writeback=False):
         import dbm
         Shelf.__init__(self, dbm.open(filename, flag), protocol, writeback)
 
+    def clear(self):
+        """Remove all items from the shelf."""
+        # Call through to the clear method on dbm-backed shelves.
+        # see https://github.com/python/cpython/issues/107089
+        self.cache.clear()
+        self.dict.clear()
+
 
 def open(filename, flag='c', protocol=None, writeback=False):
     """Open a persistent dictionary for reading and writing.

Misc/ACKS

@@ -289,6 +289,7 @@ Edward Catmur
 Lorenzo M. Catucci
 Bruno Cauet
 Donn Cave
+James Cave
 Charles Cazabon
 Jesús Cea Avión
 Per Cederqvist

Misc/NEWS.d/next/Library/2023-07-22-21-57-34.gh-issue-107089.Dnget2.rst

@@ -0,0 +1,2 @@
+Shelves opened with :func:`shelve.open` have a much faster :meth:`clear`
+method. Patch by James Cave.