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Change filterstring() and filterunicode(): If the

Browse source 
object is not a real str or unicode but an instance
of a subclass, construct the output via looping
over __getitem__. This guarantees that the result
is the same for function==None and function==lambda x:x

This doesn't happen for tuples, because filtertuple()
uses PyTuple_GetItem().

(This was discussed on SF bug #665835).
This commit is contained in:
Walter Dörwald 2003-02-10 13:19:13 +00:00
parent b4bb64e288
commit 1918f7755e
2 changed files with 74 additions and 55 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

38
Lib/test/test_builtin.py
View file

@ -418,26 +418,40 @@ def __getitem__(self, index):
def test_filter_subclasses(self):
# test, that filter() never returns tuple, str or unicode subclasses
# and that the result always go's through __getitem__
# FIXME: For tuple currently it doesn't go through __getitem__
funcs = (None, lambda x: True)
class tuple2(tuple):
pass
def __getitem__(self, index):
return 2*tuple.__getitem__(self, index)
class str2(str):
pass
def __getitem__(self, index):
return 2*str.__getitem__(self, index)
inputs = {
tuple2: [(), (1,2,3)],
str2: ["", "123"]
tuple2: {(): (), (1, 2, 3): (1, 2, 3)}, # FIXME
str2: {"": "", "123": "112233"}
}
if have_unicode:
class unicode2(unicode):
pass
inputs[unicode2] = [unicode(), unicode("123")]
def __getitem__(self, index):
return 2*unicode.__getitem__(self, index)
inputs[unicode2] = {
unicode(): unicode(),
unicode("123"): unicode("112233")
}
for func in funcs:
for (cls, inps) in inputs.iteritems():
for inp in inps:
out = filter(func, cls(inp))
self.assertEqual(inp, out)
self.assert_(not isinstance(out, cls))
for (cls, inps) in inputs.iteritems():
for (inp, exp) in inps.iteritems():
# make sure the output goes through __getitem__
# even if func is None
self.assertEqual(
filter(funcs[0], cls(inp)),
filter(funcs[1], cls(inp))
)
for func in funcs:
outp = filter(func, cls(inp))
self.assertEqual(outp, exp)
self.assert_(not isinstance(outp, cls))
def test_float(self):
self.assertEqual(float(3.14), 3.14)

91
Python/bltinmodule.c
View file

@ -1934,40 +1934,43 @@ filterstring(PyObject *func, PyObject *strobj)
int outlen = len;
if (func == Py_None) {
/* No character is ever false -- share input string
* (if it's not a subclass) */
if (PyString_CheckExact(strobj))
/* If it's a real string we can return the original,
* as no character is ever false and __getitem__
* does return this character. If it's a subclass
* we must go through the __getitem__ loop */
if (PyString_CheckExact(strobj)) {
Py_INCREF(strobj);
else
strobj = PyString_FromStringAndSize(
PyString_AS_STRING(strobj),
len
);
return strobj;
return strobj;
}
}
if ((result = PyString_FromStringAndSize(NULL, len)) == NULL)
return NULL;
for (i = j = 0; i < len; ++i) {
PyObject *item, *arg, *good;
PyObject *item;
int ok;
item = (*strobj->ob_type->tp_as_sequence->sq_item)(strobj, i);
if (item == NULL)
goto Fail_1;
arg = Py_BuildValue("(O)", item);
if (arg == NULL) {
Py_DECREF(item);
goto Fail_1;
if (func==Py_None) {
ok = 1;
} else {
PyObject *arg, *good;
arg = Py_BuildValue("(O)", item);
if (arg == NULL) {
Py_DECREF(item);
goto Fail_1;
}
good = PyEval_CallObject(func, arg);
Py_DECREF(arg);
if (good == NULL) {
Py_DECREF(item);
goto Fail_1;
}
ok = PyObject_IsTrue(good);
Py_DECREF(good);
}
good = PyEval_CallObject(func, arg);
Py_DECREF(arg);
if (good == NULL) {
Py_DECREF(item);
goto Fail_1;
}
ok = PyObject_IsTrue(good);
Py_DECREF(good);
if (ok) {
int reslen;
if (!PyString_Check(item)) {
@ -2026,16 +2029,14 @@ filterunicode(PyObject *func, PyObject *strobj)
int outlen = len;
if (func == Py_None) {
/* No character is ever false -- share input string
* (it if's not a subclass) */
if (PyUnicode_CheckExact(strobj))
/* If it's a real string we can return the original,
* as no character is ever false and __getitem__
* does return this character. If it's a subclass
* we must go through the __getitem__ loop */
if (PyUnicode_CheckExact(strobj)) {
Py_INCREF(strobj);
else
strobj = PyUnicode_FromUnicode(
PyUnicode_AS_UNICODE(strobj),
len
);
return strobj;
return strobj;
}
}
if ((result = PyUnicode_FromUnicode(NULL, len)) == NULL)
return NULL;
@ -2047,19 +2048,23 @@ filterunicode(PyObject *func, PyObject *strobj)
item = (*strobj->ob_type->tp_as_sequence->sq_item)(strobj, i);
if (item == NULL)
goto Fail_1;
arg = Py_BuildValue("(O)", item);
if (arg == NULL) {
Py_DECREF(item);
goto Fail_1;
if (func == Py_None) {
ok = 1;
} else {
arg = Py_BuildValue("(O)", item);
if (arg == NULL) {
Py_DECREF(item);
goto Fail_1;
}
good = PyEval_CallObject(func, arg);
Py_DECREF(arg);
if (good == NULL) {
Py_DECREF(item);
goto Fail_1;
}
ok = PyObject_IsTrue(good);
Py_DECREF(good);
}
good = PyEval_CallObject(func, arg);
Py_DECREF(arg);
if (good == NULL) {
Py_DECREF(item);
goto Fail_1;
}
ok = PyObject_IsTrue(good);
Py_DECREF(good);
if (ok) {
int reslen;
if (!PyUnicode_Check(item)) {