#16523: improve attrgetter/itemgetter/methodcaller documentation.
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@ -241,13 +241,22 @@ lookups. These are useful for making fast field extractors as arguments for
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expect a function argument.
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.. function:: attrgetter(attr[, args...])
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.. function:: attrgetter(attr)
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attrgetter(*attrs)
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Return a callable object that fetches *attr* from its operand. If more than one
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attribute is requested, returns a tuple of attributes. After,
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``f = attrgetter('name')``, the call ``f(b)`` returns ``b.name``. After,
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``f = attrgetter('name', 'date')``, the call ``f(b)`` returns ``(b.name,
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b.date)``. Equivalent to::
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Return a callable object that fetches *attr* from its operand.
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If more than one attribute is requested, returns a tuple of attributes.
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The attribute names can also contain dots. For example:
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* After ``f = attrgetter('name')``, the call ``f(b)`` returns ``b.name``.
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* After ``f = attrgetter('name', 'date')``, the call ``f(b)`` returns
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``(b.name, b.date)``.
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* After ``f = attrgetter('name.first', 'name.last')``, the call ``f(b)``
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returns ``(r.name.first, r.name.last)``.
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Equivalent to::
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def attrgetter(*items):
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if any(not isinstance(item, str) for item in items):
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@ -267,14 +276,19 @@ expect a function argument.
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return obj
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The attribute names can also contain dots; after ``f = attrgetter('date.month')``,
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the call ``f(b)`` returns ``b.date.month``.
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.. function:: itemgetter(item[, args...])
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.. function:: itemgetter(item)
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itemgetter(*items)
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Return a callable object that fetches *item* from its operand using the
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operand's :meth:`__getitem__` method. If multiple items are specified,
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returns a tuple of lookup values. Equivalent to::
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returns a tuple of lookup values. For example:
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* After ``f = itemgetter(2)``, the call ``f(r)`` returns ``r[2]``.
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* After ``g = itemgetter(2, 5, 3)``, the call ``g(r)`` returns
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``(r[2], r[5], r[3])``.
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Equivalent to::
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def itemgetter(*items):
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if len(items) == 1:
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@ -313,9 +327,14 @@ expect a function argument.
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Return a callable object that calls the method *name* on its operand. If
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additional arguments and/or keyword arguments are given, they will be given
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to the method as well. After ``f = methodcaller('name')``, the call ``f(b)``
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returns ``b.name()``. After ``f = methodcaller('name', 'foo', bar=1)``, the
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call ``f(b)`` returns ``b.name('foo', bar=1)``. Equivalent to::
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to the method as well. For example:
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* After ``f = methodcaller('name')``, the call ``f(b)`` returns ``b.name()``.
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* After ``f = methodcaller('name', 'foo', bar=1)``, the call ``f(b)``
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returns ``b.name('foo', bar=1)``.
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Equivalent to::
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def methodcaller(name, *args, **kwargs):
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def caller(obj):
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@ -460,8 +460,8 @@ PyDoc_STRVAR(itemgetter_doc,
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"itemgetter(item, ...) --> itemgetter object\n\
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\n\
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Return a callable object that fetches the given item(s) from its operand.\n\
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After, f=itemgetter(2), the call f(r) returns r[2].\n\
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After, g=itemgetter(2,5,3), the call g(r) returns (r[2], r[5], r[3])");
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After f = itemgetter(2), the call f(r) returns r[2].\n\
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After g = itemgetter(2, 5, 3), the call g(r) returns (r[2], r[5], r[3])");
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static PyTypeObject itemgetter_type = {
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PyVarObject_HEAD_INIT(NULL, 0)
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@ -712,9 +712,9 @@ PyDoc_STRVAR(attrgetter_doc,
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"attrgetter(attr, ...) --> attrgetter object\n\
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\n\
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Return a callable object that fetches the given attribute(s) from its operand.\n\
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After, f=attrgetter('name'), the call f(r) returns r.name.\n\
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After, g=attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
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After, h=attrgetter('name.first', 'name.last'), the call h(r) returns\n\
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After f = attrgetter('name'), the call f(r) returns r.name.\n\
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After g = attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
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After h = attrgetter('name.first', 'name.last'), the call h(r) returns\n\
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(r.name.first, r.name.last).");
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static PyTypeObject attrgetter_type = {
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@ -844,8 +844,8 @@ PyDoc_STRVAR(methodcaller_doc,
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"methodcaller(name, ...) --> methodcaller object\n\
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\n\
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Return a callable object that calls the given method on its operand.\n\
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After, f = methodcaller('name'), the call f(r) returns r.name().\n\
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After, g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
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After f = methodcaller('name'), the call f(r) returns r.name().\n\
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After g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
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r.name('date', foo=1).");
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static PyTypeObject methodcaller_type = {
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