gh-107122: Add clear method to dbm.ndbm module

Doc/library/dbm.rst

@@ -67,13 +67,13 @@
    modified by the prevailing umask).
 
 
 The object returned by :func:`.open` supports the same basic functionality as
 dictionaries; keys and their corresponding values can be stored, retrieved, and
 deleted, and the :keyword:`in` operator and the :meth:`keys` method are
 available, as well as :meth:`get` and :meth:`setdefault`.
 
 .. versionchanged:: 3.2
    :meth:`get` and :meth:`setdefault` are now available in all database modules.
 
 .. versionchanged:: 3.8
    Deleting a key from a read-only database raises database module specific error
@@ -145,7 +145,7 @@
 ``gdbm`` instead to provide some additional functionality.  Please note that the
 file formats created by :mod:`dbm.gnu` and :mod:`dbm.ndbm` are incompatible.
 
 The :mod:`dbm.gnu` module provides an interface to the GNU DBM library.
 ``dbm.gnu.gdbm`` objects behave like mappings (dictionaries), except that keys and
 values are always converted to bytes before storing.  Printing a ``gdbm``
 object doesn't print the
@@ -160,7 +160,7 @@
 
 .. function:: open(filename[, flag[, mode]])
 
    Open a ``gdbm`` database and return a :class:`gdbm` object.  The *filename*
    argument is the name of the database file.
 
    The optional *flag* argument can be:
@@ -197,7 +197,7 @@
    | ``'u'`` | Do not lock database.                      |
    +---------+--------------------------------------------+
 
    Not all flags are valid for all versions of ``gdbm``.  The module constant
    :const:`open_flags` is a string of supported flag characters.  The exception
    :exc:`error` is raised if an invalid flag is specified.
 
@@ -263,7 +263,7 @@
 
 --------------
 
 The :mod:`dbm.ndbm` module provides an interface to the Unix "(n)dbm" library.
 Dbm objects behave like mappings (dictionaries), except that keys and values are
 always stored as bytes. Printing a ``dbm`` object doesn't print the keys and
 values, and the :meth:`items` and :meth:`values` methods are not supported.
@@ -320,6 +320,12 @@
 
       Close the ``ndbm`` database.
 
+   .. method:: ndbm.clear()
+
+      Remove all items from the ``ndbm`` database.
+
+      .. versionadded:: 3.13
+
 
 :mod:`dbm.dumb` --- Portable DBM implementation
 -----------------------------------------------

Lib/test/test_dbm.py

@@ -155,6 +155,21 @@ def test_keys(self):
             self.assertNotIn(b'xxx', d)
             self.assertRaises(KeyError, lambda: d[b'xxx'])
 
+    def test_clear(self):
+        with dbm.open(_fname, 'c') as d:
+            self.assertEqual(d.keys(), [])
+            a = [(b'a', b'b'), (b'12345678910', b'019237410982340912840198242')]
+            for k, v in a:
+                d[k] = v
+            for k, _ in a:
+                self.assertIn(k, d)
+            self.assertEqual(len(d), len(a))
+
+            d.clear()
+            self.assertEqual(len(d), 0)
+            for k, _ in a:
+                self.assertNotIn(k, d)
+
     def setUp(self):
         self.addCleanup(setattr, dbm, '_defaultmod', dbm._defaultmod)
         dbm._defaultmod = self.module

Lib/test/test_dbm_ndbm.py

@@ -147,6 +147,19 @@ def test_bool_on_closed_db_raises(self):
             db['a'] = 'b'
         self.assertRaises(dbm.ndbm.error, bool, db)
 
+    def test_clear(self):
+        kvs = [('foo', 'bar'), ('1234', '5678')]
+        with dbm.ndbm.open(self.filename, 'c') as db:
+            for k, v in kvs:
+                db[k] = v
+                self.assertIn(k, db)
+            self.assertEqual(len(db), len(kvs))
+
+            db.clear()
+            for k, v in kvs:
+                self.assertNotIn(k, db)
+            self.assertEqual(len(db), 0)
+
 
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Core and Builtins/2023-07-23-21-16-54.gh-issue-107122.VNuNcq.rst

@@ -0,0 +1 @@
+Add :meth:`dbm.ndbm.clear` to :mod:`dbm.ndbm`. Patch By Dong-hee Na.

Modules/_dbmmodule.c

@@ -414,6 +414,38 @@ _dbm_dbm_setdefault_impl(dbmobject *self, PyTypeObject *cls, const char *key,
     return default_value;
 }
 
+/*[clinic input]
+_dbm.dbm.clear
+    cls: defining_class
+    /
+Remove all items from the database.
+
+[clinic start generated code]*/
+
+static PyObject *
+_dbm_dbm_clear_impl(dbmobject *self, PyTypeObject *cls)
+/*[clinic end generated code: output=8d126b9e1d01a434 input=43aa6ca1acb7f5f5]*/
+{
+    _dbm_state *state = PyType_GetModuleState(cls);
+    assert(state != NULL);
+    check_dbmobject_open(self, state->dbm_error);
+    datum key;
+    // Invalidate cache
+    self->di_size = -1;
+    while (1) {
+        key = dbm_firstkey(self->di_dbm);
+        if (key.dptr == NULL) {
+            break;
+        }
+        if (dbm_delete(self->di_dbm, key) < 0) {
+            dbm_clearerr(self->di_dbm);
+            PyErr_SetString(state->dbm_error, "cannot delete item from database");
+            return NULL;
+        }
+    }
+    Py_RETURN_NONE;
+}
+
 static PyObject *
 dbm__enter__(PyObject *self, PyObject *args)
 {
@@ -431,6 +463,7 @@ static PyMethodDef dbm_methods[] = {
     _DBM_DBM_KEYS_METHODDEF
     _DBM_DBM_GET_METHODDEF
     _DBM_DBM_SETDEFAULT_METHODDEF
+    _DBM_DBM_CLEAR_METHODDEF
     {"__enter__", dbm__enter__, METH_NOARGS, NULL},
     {"__exit__",  dbm__exit__, METH_VARARGS, NULL},
     {NULL,  NULL}           /* sentinel */