SF patch #693753: fix for bug 639806: default for dict.pop
(contributed by Michael Stone.)
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index 0006c76..1a7b505 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1104,9 +1104,10 @@
{\code{\var{a}[\var{k}]} if \code{\var{k} in \var{a}},
else \var{x} (also setting it)}
{(5)}
- \lineiii{\var{a}.pop(\var{k})}
- {remove specified \var{key} and return corresponding \var{value}}
- {}
+ \lineiii{\var{a}.pop(\var{k}\optional{, \var{x}})}
+ {\code{\var{a}[\var{k}]} if \code{\var{k} in \var{a}},
+ else \var{x} (and remove k)}
+ {(8)}
\lineiii{\var{a}.popitem()}
{remove and return an arbitrary (\var{key}, \var{value}) pair}
{(6)}
@@ -1155,6 +1156,9 @@
\item[(7)] \function{fromkeys()} is a class method that returns a
new dictionary. \var{value} defaults to \code{None}. \versionadded{2.3}
+
+\item[(8)] \function{pop()} raises a \exception{KeyError} when no default
+value is given and the key is not found. \versionadded{2.3}
\end{description}
diff --git a/Lib/UserDict.py b/Lib/UserDict.py
index fb9cdd5..6b5c9da 100644
--- a/Lib/UserDict.py
+++ b/Lib/UserDict.py
@@ -55,8 +55,8 @@
if not self.has_key(key):
self[key] = failobj
return self[key]
- def pop(self, key):
- return self.data.pop(key)
+ def pop(self, key, *args):
+ return self.data.pop(key, *args)
def popitem(self):
return self.data.popitem()
def __contains__(self, key):
@@ -117,8 +117,16 @@
except KeyError:
self[key] = default
return default
- def pop(self, key):
- value = self[key]
+ def pop(self, key, *args):
+ if len(args) > 1:
+ raise TypeError, "pop expected at most 2 arguments, got "\
+ + repr(1 + len(args))
+ try:
+ value = self[key]
+ except KeyError:
+ if args:
+ return args[0]
+ raise
del self[key]
return value
def popitem(self):
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index d571a02..f2a7ccd 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -643,10 +643,14 @@
# see SF bug #689659
x = 4503599627370496L
y = 4503599627370496
-h = {x: 'anything', y: 'something else'}
+h = {x: 'anything', y: 'something else'}
if h[x] != h[y]:
raise TestFailed, "long/int key should match"
+if d.pop(k, v) != v: raise TestFailed, "{}.pop(k, v) doesn't return default value"
+d[k] = v
+if d.pop(k, 1) != v: raise TestFailed, "{}.pop(k, v) doesn't find known key/value pair"
+
d[1] = 1
try:
for i in d:
diff --git a/Lib/test/test_userdict.py b/Lib/test/test_userdict.py
index d3e8002..cb98308 100644
--- a/Lib/test/test_userdict.py
+++ b/Lib/test/test_userdict.py
@@ -139,6 +139,9 @@
t = UserDict.UserDict(x=42)
self.assertEqual(t.pop("x"), 42)
self.assertRaises(KeyError, t.pop, "x")
+ self.assertEqual(t.pop("x", 1), 1)
+ t["x"] = 42
+ self.assertEqual(t.pop("x", 1), 42)
# Test popitem
t = UserDict.UserDict(x=42)
@@ -242,6 +245,9 @@
self.assertEqual(s.pop(10), 'ten')
self.assert_(10 not in s)
s[10] = 'ten'
+ self.assertEqual(s.pop("x", 1), 1)
+ s["x"] = 42
+ self.assertEqual(s.pop("x", 1), 42)
# popitem
k, v = s.popitem()
diff --git a/Misc/NEWS b/Misc/NEWS
index 81df415..0a446df 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,12 @@
Core and builtins
-----------------
+- dict.pop now takes an optional argument specifying a default
+ value to return if the key is not in the dict. If a default is not
+ given and the key is not found, a KeyError will still be raised.
+ Parallel changes were made to UserDict.UserDict and UserDict.DictMixin.
+ [SF patch #693753] (contributed by Michael Stone.)
+
- sys.getfilesystemencoding() was added to expose
Py_FileSystemDefaultEncoding.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index f7f2d6b..633f2ce 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1544,13 +1544,20 @@
}
static PyObject *
-dict_pop(dictobject *mp, PyObject *key)
+dict_pop(dictobject *mp, PyObject *args)
{
long hash;
dictentry *ep;
PyObject *old_value, *old_key;
+ PyObject *key, *deflt = NULL;
+ if(!PyArg_UnpackTuple(args, "pop", 1, 2, &key, &deflt))
+ return NULL;
if (mp->ma_used == 0) {
+ if (deflt) {
+ Py_INCREF(deflt);
+ return deflt;
+ }
PyErr_SetString(PyExc_KeyError,
"pop(): dictionary is empty");
return NULL;
@@ -1563,6 +1570,10 @@
}
ep = (mp->ma_lookup)(mp, key, hash);
if (ep->me_value == NULL) {
+ if (deflt) {
+ Py_INCREF(deflt);
+ return deflt;
+ }
PyErr_SetObject(PyExc_KeyError, key);
return NULL;
}
@@ -1719,7 +1730,8 @@
"D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D");
PyDoc_STRVAR(pop__doc__,
-"D.pop(k) -> v, remove specified key and return the corresponding value");
+"D.pop(k[,d]) -> v, remove specified key and return the corresponding value\n\
+If key is not found, d is returned if given, otherwise KeyError is raised");
PyDoc_STRVAR(popitem__doc__,
"D.popitem() -> (k, v), remove and return some (key, value) pair as a\n\
@@ -1763,7 +1775,7 @@
get__doc__},
{"setdefault", (PyCFunction)dict_setdefault, METH_VARARGS,
setdefault_doc__},
- {"pop", (PyCFunction)dict_pop, METH_O,
+ {"pop", (PyCFunction)dict_pop, METH_VARARGS,
pop__doc__},
{"popitem", (PyCFunction)dict_popitem, METH_NOARGS,
popitem__doc__},