Close #19282: Native context management in dbm
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@ -73,33 +73,39 @@ Key and values are always stored as bytes. This means that when
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strings are used they are implicitly converted to the default encoding before
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being stored.
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These objects also support being used in a :keyword:`with` statement, which
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will automatically close them when done.
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.. versionchanged:: 3.4
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Added native support for the context management protocol to the objects
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returned by :func:`.open`.
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The following example records some hostnames and a corresponding title, and
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then prints out the contents of the database::
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import dbm
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# Open database, creating it if necessary.
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db = dbm.open('cache', 'c')
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with dbm.open('cache', 'c') as db:
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# Record some values
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db[b'hello'] = b'there'
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db['www.python.org'] = 'Python Website'
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db['www.cnn.com'] = 'Cable News Network'
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# Record some values
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db[b'hello'] = b'there'
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db['www.python.org'] = 'Python Website'
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db['www.cnn.com'] = 'Cable News Network'
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# Note that the keys are considered bytes now.
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assert db[b'www.python.org'] == b'Python Website'
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# Notice how the value is now in bytes.
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assert db['www.cnn.com'] == b'Cable News Network'
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# Note that the keys are considered bytes now.
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assert db[b'www.python.org'] == b'Python Website'
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# Notice how the value is now in bytes.
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assert db['www.cnn.com'] == b'Cable News Network'
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# Often-used methods of the dict interface work too.
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print(db.get('python.org', b'not present'))
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# Often-used methods of the dict interface work too.
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print(db.get('python.org', b'not present'))
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# Storing a non-string key or value will raise an exception (most
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# likely a TypeError).
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db['www.yahoo.com'] = 4
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# Storing a non-string key or value will raise an exception (most
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# likely a TypeError).
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db['www.yahoo.com'] = 4
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# Close when done.
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db.close()
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# db is automatically closed when leaving the with statement.
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.. seealso::
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@ -236,6 +236,12 @@ class _Database(collections.MutableMapping):
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if hasattr(self._os, 'chmod'):
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self._os.chmod(file, self._mode)
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def __enter__(self):
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return self
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def __exit__(self, *args):
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self.close()
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def open(file, flag=None, mode=0o666):
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"""Open the database file, filename, and return corresponding object.
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@ -184,6 +184,19 @@ class DumbDBMTestCase(unittest.TestCase):
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self.assertEqual(expected, got)
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f.close()
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def test_context_manager(self):
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with dumbdbm.open(_fname, 'c') as db:
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db["dumbdbm context manager"] = "context manager"
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with dumbdbm.open(_fname, 'r') as db:
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self.assertEqual(list(db.keys()), [b"dumbdbm context manager"])
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# This currently just raises AttributeError rather than a specific
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# exception like the GNU or NDBM based implementations. See
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# http://bugs.python.org/issue19385 for details.
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with self.assertRaises(Exception):
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db.keys()
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def tearDown(self):
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_delete_files()
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@ -81,6 +81,17 @@ class TestGdbm(unittest.TestCase):
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size2 = os.path.getsize(filename)
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self.assertTrue(size1 > size2 >= size0)
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def test_context_manager(self):
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with gdbm.open(filename, 'c') as db:
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db["gdbm context manager"] = "context manager"
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with gdbm.open(filename, 'r') as db:
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self.assertEqual(list(db.keys()), [b"gdbm context manager"])
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with self.assertRaises(gdbm.error) as cm:
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db.keys()
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self.assertEqual(str(cm.exception),
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"GDBM object has already been closed")
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if __name__ == '__main__':
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unittest.main()
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@ -37,5 +37,18 @@ class DbmTestCase(unittest.TestCase):
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except error:
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self.fail()
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def test_context_manager(self):
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with dbm.ndbm.open(self.filename, 'c') as db:
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db["ndbm context manager"] = "context manager"
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with dbm.ndbm.open(self.filename, 'r') as db:
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self.assertEqual(list(db.keys()), [b"ndbm context manager"])
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with self.assertRaises(dbm.ndbm.error) as cm:
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db.keys()
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self.assertEqual(str(cm.exception),
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"DBM object has already been closed")
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if __name__ == '__main__':
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unittest.main()
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@ -50,6 +50,9 @@ Core and Builtins
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Library
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-------
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- Issue #19282: dbm.open now supports the context manager protocol. (Inital
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patch by Claudiu Popa)
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- Issue #8311: Added support for writing any bytes-like objects in the aifc,
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sunau, and wave modules.
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@ -313,6 +313,21 @@ dbm_setdefault(dbmobject *dp, PyObject *args)
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return defvalue;
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}
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static PyObject *
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dbm__enter__(PyObject *self, PyObject *args)
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{
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Py_INCREF(self);
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return self;
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}
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static PyObject *
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dbm__exit__(PyObject *self, PyObject *args)
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{
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_Py_IDENTIFIER(close);
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return _PyObject_CallMethodId(self, &PyId_close, NULL);
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}
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static PyMethodDef dbm_methods[] = {
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{"close", (PyCFunction)dbm__close, METH_NOARGS,
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"close()\nClose the database."},
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@ -325,6 +340,8 @@ static PyMethodDef dbm_methods[] = {
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"setdefault(key[, default]) -> value\n"
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"Return the value for key if present, otherwise default. If key\n"
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"is not in the database, it is inserted with default as the value."},
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{"__enter__", dbm__enter__, METH_NOARGS, NULL},
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{"__exit__", dbm__exit__, METH_VARARGS, NULL},
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{NULL, NULL} /* sentinel */
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};
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@ -425,6 +425,20 @@ dbm_sync(dbmobject *dp, PyObject *unused)
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return Py_None;
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}
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static PyObject *
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dbm__enter__(PyObject *self, PyObject *args)
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{
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Py_INCREF(self);
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return self;
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}
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static PyObject *
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dbm__exit__(PyObject *self, PyObject *args)
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{
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_Py_IDENTIFIER(close);
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return _PyObject_CallMethodId(self, &PyId_close, NULL);
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}
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static PyMethodDef dbm_methods[] = {
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{"close", (PyCFunction)dbm_close, METH_NOARGS, dbm_close__doc__},
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{"keys", (PyCFunction)dbm_keys, METH_NOARGS, dbm_keys__doc__},
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@ -434,6 +448,8 @@ static PyMethodDef dbm_methods[] = {
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{"sync", (PyCFunction)dbm_sync, METH_NOARGS, dbm_sync__doc__},
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{"get", (PyCFunction)dbm_get, METH_VARARGS, dbm_get__doc__},
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{"setdefault",(PyCFunction)dbm_setdefault,METH_VARARGS, dbm_setdefault__doc__},
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{"__enter__", dbm__enter__, METH_NOARGS, NULL},
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{"__exit__", dbm__exit__, METH_VARARGS, NULL},
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{NULL, NULL} /* sentinel */
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};
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