Issue 2778. Document the temporary frozenset swap in __contains__(), remove(), and discard().

This commit is contained in:
Raymond Hettinger 2008-05-08 17:18:13 +00:00
parent bf5bd9f2f0
commit f8105ceec7
1 changed files with 12 additions and 9 deletions

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@ -1585,7 +1585,7 @@ proper superset of the second set (is a superset, but is not equal).
Instances of :class:`set` are compared to instances of :class:`frozenset` based
on their members. For example, ``set('abc') == frozenset('abc')`` returns
``True``.
``True`` and so does ``set('abc') in set([frozenset('abc')])``.
The subset and equality comparisons do not generalize to a complete ordering
function. For example, any two disjoint sets are not equal and are not subsets
@ -1624,18 +1624,18 @@ apply to immutable instances of :class:`frozenset`:
Update the set, keeping only elements found in either set, but not in both.
.. method:: set.add(el)
.. method:: set.add(elem)
Add element *el* to the set.
Add element *elem* to the set.
.. method:: set.remove(el)
.. method:: set.remove(elem)
Remove element *el* from the set. Raises :exc:`KeyError` if *el* is not
Remove element *elem* from the set. Raises :exc:`KeyError` if *elem* is not
contained in the set.
.. method:: set.discard(el)
.. method:: set.discard(elem)
Remove element *el* from the set if it is present.
Remove element *elem* from the set if it is present.
.. method:: set.pop()
@ -1652,8 +1652,11 @@ Note, the non-operator versions of the :meth:`update`,
:meth:`symmetric_difference_update` methods will accept any iterable as an
argument.
The design of the set types was based on lessons learned from the Python
implementation found in the :mod:`sets` module.
Note, the *elem* argument to the :meth:`__contains__`, :meth:`remove`, and
:meth:`discard` methods may be a set. To support searching for an equivalent
frozenset, the *elem* set is temporarily mutated during the search and then
restored. During the search, the *elem* set should not be read or mutated
since it does not have a meaningful value.
.. seealso::