#16523: improve attrgetter/itemgetter/methodcaller documentation.

Doc/library/operator.rst

@@ -241,13 +241,22 @@ lookups.  These are useful for making fast field extractors as arguments for
 expect a function argument.
 
 
-.. function:: attrgetter(attr[, args...])
+.. function:: attrgetter(attr)
+              attrgetter(*attrs)
 
-   Return a callable object that fetches *attr* from its operand. If more than one
+   Return a callable object that fetches *attr* from its operand.
-   attribute is requested, returns a tuple of attributes. After,
+   If more than one attribute is requested, returns a tuple of attributes.
-   ``f = attrgetter('name')``, the call ``f(b)`` returns ``b.name``.  After,
+   The attribute names can also contain dots. For example:
-   ``f = attrgetter('name', 'date')``, the call ``f(b)`` returns ``(b.name,
+
-   b.date)``.  Equivalent to::
+   * After ``f = attrgetter('name')``, the call ``f(b)`` returns ``b.name``.
+
+   * After ``f = attrgetter('name', 'date')``, the call ``f(b)`` returns
+     ``(b.name, b.date)``.
+
+   * After ``f = attrgetter('name.first', 'name.last')``, the call ``f(b)``
+     returns ``(r.name.first, r.name.last)``.
+
+   Equivalent to::
 
       def attrgetter(*items):
           if any(not isinstance(item, str) for item in items):
@@ -267,14 +276,19 @@ expect a function argument.
           return obj
 
 
-   The attribute names can also contain dots; after ``f = attrgetter('date.month')``,
+.. function:: itemgetter(item)
-   the call ``f(b)`` returns ``b.date.month``.
+              itemgetter(*items)
-
-.. function:: itemgetter(item[, args...])
 
    Return a callable object that fetches *item* from its operand using the
    operand's :meth:`__getitem__` method.  If multiple items are specified,
-   returns a tuple of lookup values.  Equivalent to::
+   returns a tuple of lookup values.  For example:
+
+   * After ``f = itemgetter(2)``, the call ``f(r)`` returns ``r[2]``.
+
+   * After ``g = itemgetter(2, 5, 3)``, the call ``g(r)`` returns
+     ``(r[2], r[5], r[3])``.
+
+   Equivalent to::
 
       def itemgetter(*items):
           if len(items) == 1:
@@ -313,9 +327,14 @@ expect a function argument.
 
    Return a callable object that calls the method *name* on its operand.  If
    additional arguments and/or keyword arguments are given, they will be given
-   to the method as well.  After ``f = methodcaller('name')``, the call ``f(b)``
+   to the method as well.  For example:
-   returns ``b.name()``.  After ``f = methodcaller('name', 'foo', bar=1)``, the
+
-   call ``f(b)`` returns ``b.name('foo', bar=1)``.  Equivalent to::
+   * After ``f = methodcaller('name')``, the call ``f(b)`` returns ``b.name()``.
+
+   * After ``f = methodcaller('name', 'foo', bar=1)``, the call ``f(b)``
+     returns ``b.name('foo', bar=1)``.
+
+   Equivalent to::
 
       def methodcaller(name, *args, **kwargs):
           def caller(obj):

Modules/operator.c

@@ -460,8 +460,8 @@ PyDoc_STRVAR(itemgetter_doc,
 "itemgetter(item, ...) --> itemgetter object\n\
 \n\
 Return a callable object that fetches the given item(s) from its operand.\n\
-After, f=itemgetter(2), the call f(r) returns r[2].\n\
+After f = itemgetter(2), the call f(r) returns r[2].\n\
-After, g=itemgetter(2,5,3), the call g(r) returns (r[2], r[5], r[3])");
+After g = itemgetter(2, 5, 3), the call g(r) returns (r[2], r[5], r[3])");
 
 static PyTypeObject itemgetter_type = {
     PyVarObject_HEAD_INIT(NULL, 0)
@@ -712,9 +712,9 @@ PyDoc_STRVAR(attrgetter_doc,
 "attrgetter(attr, ...) --> attrgetter object\n\
 \n\
 Return a callable object that fetches the given attribute(s) from its operand.\n\
-After, f=attrgetter('name'), the call f(r) returns r.name.\n\
+After f = attrgetter('name'), the call f(r) returns r.name.\n\
-After, g=attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
+After g = attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
-After, h=attrgetter('name.first', 'name.last'), the call h(r) returns\n\
+After h = attrgetter('name.first', 'name.last'), the call h(r) returns\n\
 (r.name.first, r.name.last).");
 
 static PyTypeObject attrgetter_type = {
@@ -844,8 +844,8 @@ PyDoc_STRVAR(methodcaller_doc,
 "methodcaller(name, ...) --> methodcaller object\n\
 \n\
 Return a callable object that calls the given method on its operand.\n\
-After, f = methodcaller('name'), the call f(r) returns r.name().\n\
+After f = methodcaller('name'), the call f(r) returns r.name().\n\
-After, g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
+After g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
 r.name('date', foo=1).");
 
 static PyTypeObject methodcaller_type = {