PEP 3101: Completed string.Formatter class. Reimplemented field_name to object transformation.

Include/unicodeobject.h

@@ -1440,8 +1440,7 @@ PyAPI_FUNC(Py_UNICODE*) Py_UNICODE_strchr(
 PyObject *
 _unicodeformatter_iterator(PyObject *str);
 PyObject *
-_unicodeformatter_lookup(PyObject *field_name, PyObject *args,
-                         PyObject *kwargs);
+_unicodeformatter_field_name_split(PyObject *field_name);
 
 #ifdef __cplusplus
 }

Lib/string.py

@@ -200,31 +200,59 @@ class Template(metaclass=_TemplateMetaclass):
 # exposed here via the sys module.  sys was chosen because it's always
 # available and doesn't have to be dynamically loaded.
 
-# The parser is implemented in sys._formatter_parser.
-# The "object lookup" is implemented in sys._formatter_lookup
+# The overall parser is implemented in sys._formatter_parser.
+# The field name parser is implemented in sys._formatter_field_name_split
 
-from sys import _formatter_parser, _formatter_lookup
+from sys import _formatter_parser, _formatter_field_name_split
 
 class Formatter:
     def format(self, format_string, *args, **kwargs):
         return self.vformat(format_string, args, kwargs)
 
     def vformat(self, format_string, args, kwargs):
+        used_args = set()
         result = []
         for (is_markup, literal, field_name, format_spec, conversion) in \
                 _formatter_parser(format_string):
             if is_markup:
-                # find the object
-                index, name, obj = _formatter_lookup(field_name, args, kwargs)
+                # given the field_name, find the object it references
+
+                # split it into the first part, and and iterator that
+                #  looks over the rest
+                first, rest = _formatter_field_name_split(field_name)
+
+                used_args.add(first)
+                obj = self.get_value(first, args, kwargs)
+
+                # loop through the rest of the field_name, doing
+                #  getattr or getitem as needed
+                for is_attr, i in rest:
+                    if is_attr:
+                        obj = getattr(obj, i)
+                    else:
+                        obj = obj[i]
+
+                # do any conversion on the resulting object
+                if conversion == 'r':
+                    obj = repr(obj)
+                elif conversion == 's':
+                    obj = str(obj)
+
+                # format the object and append to the result
+                result.append(self.format_field(obj, format_spec))
             else:
                 result.append(literal)
+        self.check_unused_args(used_args, args, kwargs)
         return ''.join(result)
 
     def get_value(self, key, args, kwargs):
-        pass
+        if isinstance(key, int):
+            return args[key]
+        else:
+            return kwargs[key]
 
     def check_unused_args(self, used_args, args, kwargs):
         pass
 
     def format_field(self, value, format_spec):
-        pass
+        return format(value, format_spec)

Lib/test/test_string.py

@@ -19,8 +19,27 @@ class ModuleTest(unittest.TestCase):
         fmt = string.Formatter()
         self.assertEqual(fmt.format("foo"), "foo")
 
-        # Formatter not working you for lookups
-        #self.assertEqual(fmt.format("foo{0}", "bar"), "foobar")
+        self.assertEqual(fmt.format("foo{0}", "bar"), "foobar")
+        self.assertEqual(fmt.format("foo{1}{0}-{1}", "bar", 6), "foo6bar-6")
+        self.assertEqual(fmt.format("-{arg!r}-", arg='test'), "-'test'-")
+
+        class NamespaceFormatter(string.Formatter):
+            def __init__(self, namespace={}):
+                string.Formatter.__init__(self)
+                self.namespace = namespace
+
+            def get_value(self, key, args, kwds):
+                if isinstance(key, str):
+                    try:
+                        # Check explicitly passed arguments first
+                        return kwds[key]
+                    except KeyError:
+                        return self.namespace[key]
+                else:
+                    string.Formatter.get_value(key, args, kwds)
+
+        fmt = NamespaceFormatter({'greeting':'hello'})
+        self.assertEqual(fmt.format("{greeting}, world!"), 'hello, world!')
 
 
     def test_maketrans(self):

Lib/test/test_unicode.py

@@ -449,6 +449,10 @@ class UnicodeTest(
         self.assertEqual('}}{{'.format(), '}{')
         self.assertEqual('}}x{{'.format(), '}x{')
 
+        # weird field names
+        self.assertEqual("{0[foo-bar]}".format({'foo-bar':'baz'}), 'baz')
+        self.assertEqual("{0[foo bar]}".format({'foo bar':'baz'}), 'baz')
+
         self.assertEqual('{foo._x}'.format(foo=C(20)), '20')
         self.assertEqual('{1}{0}'.format(D(10), D(20)), '2010')
         self.assertEqual('{0._x.x}'.format(C(D('abc'))), 'abc')
@@ -539,7 +543,11 @@ class UnicodeTest(
         self.assertRaises(ValueError, "}".format)
         self.assertRaises(ValueError, "abc{0:{}".format)
         self.assertRaises(ValueError, "{0".format)
+        self.assertRaises(ValueError, "{0.}".format)
+        self.assertRaises(ValueError, "{0[}".format)
+        self.assertRaises(ValueError, "{0]}".format)
         self.assertRaises(ValueError, "{0.[]}".format)
+        self.assertRaises(ValueError, "{0..foo}".format, 0)
         self.assertRaises(ValueError, "{0[0}".format)
         self.assertRaises(ValueError, "{0[0:foo}".format)
         self.assertRaises(ValueError, "{c]}".format)
@@ -551,6 +559,7 @@ class UnicodeTest(
         self.assertRaises(ValueError, "{0!rs}".format)
         self.assertRaises(ValueError, "{!}".format)
         self.assertRaises(ValueError, "{:}".format)
+        self.assertRaises(ValueError, "{:s}".format)
         self.assertRaises(ValueError, "{}".format)
 
         # can't have a replacement on the field name portion

Objects/unicodeobject.c

@@ -9161,9 +9161,8 @@ typedef struct {
 static void
 formatteriter_dealloc(formatteriterobject *it)
 {
-	_PyObject_GC_UNTRACK(it);
-	Py_XDECREF(it->str);
-	PyObject_GC_Del(it);
+        Py_XDECREF(it->str);
+	PyObject_FREE(it);
 }
 
 /* returns a tuple:
@@ -9313,7 +9312,7 @@ _unicodeformatter_iterator(PyObject *str)
 {
         formatteriterobject *it;
 
-	it = PyObject_GC_New(formatteriterobject, &PyFormatterIter_Type);
+	it = PyObject_New(formatteriterobject, &PyFormatterIter_Type);
 	if (it == NULL)
 		return NULL;
 
@@ -9326,17 +9325,167 @@ _unicodeformatter_iterator(PyObject *str)
                             PyUnicode_AS_UNICODE(str),
                             PyUnicode_GET_SIZE(str));
 
-	_PyObject_GC_TRACK(it);
 	return (PyObject *)it;
 }
 
-PyObject *
-_unicodeformatter_lookup(PyObject *field_name, PyObject *args,
-                         PyObject *kwargs)
+/********************* FieldName Iterator ************************/
+
+/* this is used to implement string.Formatter.vparse().  it parses
+   the field name into attribute and item values. */
+
+typedef struct {
+	PyObject_HEAD
+
+        /* we know this to be a unicode object, but since we just keep
+           it around to keep the object alive, having it as PyObject
+           is okay */
+        PyObject *str;
+
+        FieldNameIterator it_field;
+} fieldnameiterobject;
+
+static void
+fieldnameiter_dealloc(fieldnameiterobject *it)
 {
+        Py_XDECREF(it->str);
+	PyObject_FREE(it);
+}
+
+/* returns a tuple:
+   (is_attr, value)
+   is_attr is true if we used attribute syntax (e.g., '.foo')
+              false if we used index syntax (e.g., '[foo]')
+   value is an integer or string
+*/
+static PyObject *
+fieldnameiter_next(fieldnameiterobject *it)
+{
+        int result;
+        int is_attr;
+        Py_ssize_t idx;
+        SubString name;
+
+        result = FieldNameIterator_next(&it->it_field, &is_attr,
+                                            &idx, &name);
+        if (result == 0 || result == 1) {
+                /* if 0, error has already been set, if 1, iterator is empty */
+                return NULL;
+        } else {
+                PyObject* result = NULL;
+                PyObject* is_attr_obj = NULL;
+                PyObject* obj = NULL;
+
+                is_attr_obj = PyBool_FromLong(is_attr);
+                if (is_attr_obj == NULL)
+                        goto error;
+
+                /* either an integer or a string */
+                if (idx != -1)
+                        obj = PyInt_FromSsize_t(idx);
+                else
+                        obj = STRINGLIB_NEW(name.ptr, name.end - name.ptr);
+                if (obj == NULL)
+                        goto error;
+
+               /* return a tuple of values */
+                result = PyTuple_Pack(2, is_attr_obj, obj);
+                if (result == NULL)
+                        goto error;
+
+                return result;
+
+        error:
+                Py_XDECREF(result);
+                Py_XDECREF(is_attr_obj);
+                Py_XDECREF(obj);
+                return NULL;
+        }
         return NULL;
 }
 
+static PyMethodDef fieldnameiter_methods[] = {
+ 	{NULL,		NULL}		/* sentinel */
+};
+
+static PyTypeObject PyFieldNameIter_Type = {
+	PyVarObject_HEAD_INIT(&PyType_Type, 0)
+	"fieldnameiterator",			/* tp_name */
+	sizeof(fieldnameiterobject),		/* tp_basicsize */
+	0,					/* tp_itemsize */
+	/* methods */
+	(destructor)fieldnameiter_dealloc,	/* tp_dealloc */
+	0,					/* tp_print */
+	0,					/* tp_getattr */
+	0,					/* tp_setattr */
+	0,					/* tp_compare */
+	0,					/* tp_repr */
+	0,					/* tp_as_number */
+	0,					/* tp_as_sequence */
+	0,					/* tp_as_mapping */
+	0,					/* tp_hash */
+	0,					/* tp_call */
+	0,					/* tp_str */
+	PyObject_GenericGetAttr,		/* tp_getattro */
+	0,					/* tp_setattro */
+	0,					/* tp_as_buffer */
+	Py_TPFLAGS_DEFAULT,			/* tp_flags */
+	0,					/* tp_doc */
+	0,					/* tp_traverse */
+	0,					/* tp_clear */
+	0,					/* tp_richcompare */
+	0,					/* tp_weaklistoffset */
+	PyObject_SelfIter,			/* tp_iter */
+	(iternextfunc)fieldnameiter_next,	/* tp_iternext */
+	fieldnameiter_methods,			/* tp_methods */
+        0};
+
+PyObject *
+_unicodeformatter_field_name_split(PyObject *field_name)
+{
+        SubString first;
+        Py_ssize_t first_idx;
+        fieldnameiterobject *it;
+
+        PyObject *first_obj = NULL;
+        PyObject *it_obj = NULL;
+        PyObject *result;
+
+        it = PyObject_New(fieldnameiterobject, &PyFieldNameIter_Type);
+        if (it == NULL)
+                goto error;
+        it->str = NULL;
+        it_obj = (PyObject *)it;
+
+        if (!field_name_split(STRINGLIB_STR(field_name),
+                              STRINGLIB_LEN(field_name),
+                              &first, &first_idx, &it->it_field))
+                goto error;
+
+        /* first becomes an integer, if possible, else a string */
+        if (first_idx != -1)
+                first_obj = PyInt_FromSsize_t(first_idx);
+        else
+                /* convert "first" into a string object */
+                first_obj = STRINGLIB_NEW(first.ptr, first.end - first.ptr);
+        if (first_obj == NULL)
+                goto error;
+
+        /* take ownership, give the object to the iterator.  this is
+           just to keep the field_name alive */
+        Py_INCREF(field_name);
+        it->str = field_name;
+
+        /* return a tuple of values */
+        result = PyTuple_Pack(2, first_obj, it_obj);
+        if (result == NULL)
+                goto error;
+
+        return result;
+error:
+        Py_XDECREF(it_obj);
+        Py_XDECREF(first_obj);
+        return NULL;
+}
 
 /********************* Unicode Iterator **************************/
 

Python/sysmodule.c

@@ -683,28 +683,28 @@ sys_formatter_iterator(PyObject *self, PyObject *args)
         return _unicodeformatter_iterator(str);
 }
 
-/* sys_formatter_lookup is used to implement string.Formatter.vformat.
-   it takes an PEP 3101 "field name", args, and kwargs, and returns a
-   tuple (index, name, object).  see unicodeobject.c's
-   _unicodeformatter_lookup for details */
+/* sys_formatter_field_name_split is used to implement
+   string.Formatter.vformat.  it takes an PEP 3101 "field name", and
+   returns a tuple of (first, rest): "first", the part before the
+   first '.' or '['; and "rest", an iterator for the rest of the field
+   name.  see unicodeobjects' _unicode_formatter_field_name_split for
+   details */
 static PyObject *
-sys_formatter_lookup(PyObject *self, PyObject *args)
+sys_formatter_field_name_split(PyObject *self, PyObject *args)
 {
         PyObject *field_name;
-        PyObject *arg_args;
-        PyObject *kwargs;
 
-        if (!PyArg_ParseTuple(args, "OOO:_formatter_lookup", &field_name,
-                              &arg_args, &kwargs))
+        if (!PyArg_ParseTuple(args, "O:_formatter_field_name_split",
+                              &field_name))
                 return NULL;
 
         if (!PyUnicode_Check(field_name)) {
-                PyErr_SetString(PyExc_TypeError,
-                                "_formatter_lookup expects unicode object");
+                PyErr_SetString(PyExc_TypeError, "_formatter_field_name_split "
+                                "expects unicode object");
                 return NULL;
         }
 
-        return _unicodeformatter_lookup(field_name, arg_args, kwargs);
+        return _unicodeformatter_field_name_split(field_name);
 }
 
 
@@ -773,7 +773,8 @@ static PyMethodDef sys_methods[] = {
 	{"_current_frames", sys_current_frames, METH_NOARGS,
 	 current_frames_doc},
         {"_formatter_parser", sys_formatter_iterator, METH_VARARGS},
-        {"_formatter_lookup", sys_formatter_lookup, METH_VARARGS},
+        {"_formatter_field_name_split", sys_formatter_field_name_split,
+         METH_VARARGS},
 	{"displayhook",	sys_displayhook, METH_O, displayhook_doc},
 	{"exc_info",	sys_exc_info, METH_NOARGS, exc_info_doc},
 	{"excepthook",	sys_excepthook, METH_VARARGS, excepthook_doc},