sets, the inner sets must be :class:`frozenset` objects. If *iterable* is
not specified, a new empty set is returned.
-Instances of :class:`set` and :class:`frozenset` provide the following
-operations:
+ Instances of :class:`set` and :class:`frozenset` provide the following
+ operations:
-.. describe:: len(s)
+ .. describe:: len(s)
- Return the cardinality of set *s*.
+ Return the cardinality of set *s*.
-.. describe:: x in s
+ .. describe:: x in s
- Test *x* for membership in *s*.
+ Test *x* for membership in *s*.
-.. describe:: x not in s
+ .. describe:: x not in s
- Test *x* for non-membership in *s*.
+ Test *x* for non-membership in *s*.
-.. method:: set.isdisjoint(other)
+ .. method:: isdisjoint(other)
- Return True if the set has no elements in common with *other*.
- Sets are disjoint if and only if their interesection is the empty set.
+ Return True if the set has no elements in common with *other*. Sets are
+ disjoint if and only if their interesection is the empty set.
- .. versionadded:: 2.6
+ .. versionadded:: 2.6
-.. method:: set.issubset(other)
- set <= other
+ .. method:: issubset(other)
+ set <= other
- Test whether every element in the set is in *other*.
+ Test whether every element in the set is in *other*.
-.. method:: set < other
+ .. method:: set < other
- Test whether the set is a true subset of *other*, that is,
- ``set <= other and set != other``.
+ Test whether the set is a true subset of *other*, that is,
+ ``set <= other and set != other``.
-.. method:: set.issuperset(other)
- set >= other
+ .. method:: issuperset(other)
+ set >= other
- Test whether every element in *other* is in the set.
+ Test whether every element in *other* is in the set.
-.. method:: set > other
+ .. method:: set > other
- Test whether the set is a true superset of *other*, that is,
- ``set >= other and set != other``.
+ Test whether the set is a true superset of *other*, that is, ``set >=
+ other and set != other``.
-.. method:: set.union(other)
- set | other
+ .. method:: union(other)
+ set | other
- Return a new set with elements from both sets.
+ Return a new set with elements from both sets.
-.. method:: set.intersection(other)
- set & other
+ .. method:: intersection(other)
+ set & other
- Return a new set with elements common to both sets.
+ Return a new set with elements common to both sets.
-.. method:: set.difference(other)
- set - other
+ .. method:: difference(other)
+ set - other
- Return a new set with elements in the set that are not in *other*.
+ Return a new set with elements in the set that are not in *other*.
-.. method:: set.symmetric_difference(other)
- set ^ other
+ .. method:: symmetric_difference(other)
+ set ^ other
- Return a new set with elements in either the set or *other* but not both.
+ Return a new set with elements in either the set or *other* but not both.
-.. method:: set.copy()
+ .. method:: copy()
- Return a new set with a shallow copy of *s*.
+ Return a new set with a shallow copy of *s*.
-Note, the non-operator versions of :meth:`union`, :meth:`intersection`,
-:meth:`difference`, and :meth:`symmetric_difference`, :meth:`issubset`, and
-:meth:`issuperset` methods will accept any iterable as an argument. In
-contrast, their operator based counterparts require their arguments to be sets.
-This precludes error-prone constructions like ``set('abc') & 'cbs'`` in favor of
-the more readable ``set('abc').intersection('cbs')``.
+ Note, the non-operator versions of :meth:`union`, :meth:`intersection`,
+ :meth:`difference`, and :meth:`symmetric_difference`, :meth:`issubset`, and
+ :meth:`issuperset` methods will accept any iterable as an argument. In
+ contrast, their operator based counterparts require their arguments to be
+ sets. This precludes error-prone constructions like ``set('abc') & 'cbs'``
+ in favor of the more readable ``set('abc').intersection('cbs')``.
-Both :class:`set` and :class:`frozenset` support set to set comparisons. Two
-sets are equal if and only if every element of each set is contained in the
-other (each is a subset of the other). A set is less than another set if and
-only if the first set is a proper subset of the second set (is a subset, but is
-not equal). A set is greater than another set if and only if the first set is a
-proper superset of the second set (is a superset, but is not equal).
+ Both :class:`set` and :class:`frozenset` support set to set comparisons. Two
+ sets are equal if and only if every element of each set is contained in the
+ other (each is a subset of the other). A set is less than another set if and
+ only if the first set is a proper subset of the second set (is a subset, but
+ is not equal). A set is greater than another set if and only if the first set
+ is a 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`` and so does ``set('abc') in set([frozenset('abc')])``.
+ Instances of :class:`set` are compared to instances of :class:`frozenset`
+ based on their members. For example, ``set('abc') == frozenset('abc')``
+ returns ``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
-of each other, so *all* of the following return ``False``: ``a<b``, ``a==b``,
-or ``a>b``. Accordingly, sets do not implement the :meth:`__cmp__` method.
+ 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 of each other, so *all* of the following return ``False``: ``a<b``,
+ ``a==b``, or ``a>b``. Accordingly, sets do not implement the :meth:`__cmp__`
+ method.
-Since sets only define partial ordering (subset relationships), the output of
-the :meth:`list.sort` method is undefined for lists of sets.
+ Since sets only define partial ordering (subset relationships), the output of
+ the :meth:`list.sort` method is undefined for lists of sets.
-Set elements, like dictionary keys, must be :term:`hashable`.
+ Set elements, like dictionary keys, must be :term:`hashable`.
-Binary operations that mix :class:`set` instances with :class:`frozenset` return
-the type of the first operand. For example: ``frozenset('ab') | set('bc')``
-returns an instance of :class:`frozenset`.
+ Binary operations that mix :class:`set` instances with :class:`frozenset`
+ return the type of the first operand. For example: ``frozenset('ab') |
+ set('bc')`` returns an instance of :class:`frozenset`.
-The following table lists operations available for :class:`set` that do not
-apply to immutable instances of :class:`frozenset`:
+ The following table lists operations available for :class:`set` that do not
+ apply to immutable instances of :class:`frozenset`:
-.. method:: set.update(other)
- set |= other
+ .. method:: update(other)
+ set |= other
- Update the set, adding elements from *other*.
+ Update the set, adding elements from *other*.
-.. method:: set.intersection_update(other)
- set &= other
+ .. method:: intersection_update(other)
+ set &= other
- Update the set, keeping only elements found in it and *other*.
+ Update the set, keeping only elements found in it and *other*.
-.. method:: set.difference_update(other)
- set -= other
+ .. method:: difference_update(other)
+ set -= other
- Update the set, removing elements found in *other*.
+ Update the set, removing elements found in *other*.
-.. method:: set.symmetric_difference_update(other)
- set ^= other
+ .. method:: symmetric_difference_update(other)
+ set ^= other
- Update the set, keeping only elements found in either set, but not in both.
+ Update the set, keeping only elements found in either set, but not in both.
-.. method:: set.add(elem)
+ .. method:: add(elem)
- Add element *elem* to the set.
+ Add element *elem* to the set.
-.. method:: set.remove(elem)
+ .. method:: remove(elem)
- Remove element *elem* from the set. Raises :exc:`KeyError` if *elem* is not
- contained in the set.
+ Remove element *elem* from the set. Raises :exc:`KeyError` if *elem* is
+ not contained in the set.
-.. method:: set.discard(elem)
+ .. method:: discard(elem)
- Remove element *elem* from the set if it is present.
+ Remove element *elem* from the set if it is present.
-.. method:: set.pop()
+ .. method:: pop()
- Remove and return an arbitrary element from the set. Raises :exc:`KeyError`
- if the set is empty.
+ Remove and return an arbitrary element from the set. Raises
+ :exc:`KeyError` if the set is empty.
-.. method:: set.clear()
+ .. method:: clear()
- Remove all elements from the set.
+ Remove all elements from the set.
-Note, the non-operator versions of the :meth:`update`,
-:meth:`intersection_update`, :meth:`difference_update`, and
-:meth:`symmetric_difference_update` methods will accept any iterable as an
-argument.
+ Note, the non-operator versions of the :meth:`update`,
+ :meth:`intersection_update`, :meth:`difference_update`, and
+ :meth:`symmetric_difference_update` methods will accept any iterable as an
+ argument.
-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.
+ 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::
Support for building a dictionary from keyword arguments added.
-These are the operations that dictionaries support (and therefore, custom mapping
-types should support too):
+ These are the operations that dictionaries support (and therefore, custom
+ mapping types should support too):
-.. describe:: len(d)
+ .. describe:: len(d)
- Return the number of items in the dictionary *d*.
+ Return the number of items in the dictionary *d*.
-.. describe:: d[key]
+ .. describe:: d[key]
- Return the item of *d* with key *key*. Raises a :exc:`KeyError` if *key* is
- not in the map.
-
- .. versionadded:: 2.5
- If a subclass of dict defines a method :meth:`__missing__`, if the key
- *key* is not present, the ``d[key]`` operation calls that method with the
- key *key* as argument. The ``d[key]`` operation then returns or raises
- whatever is returned or raised by the ``__missing__(key)`` call if the key
- is not present. No other operations or methods invoke
- :meth:`__missing__`. If :meth:`__missing__` is not defined,
- :exc:`KeyError` is raised. :meth:`__missing__` must be a method; it
- cannot be an instance variable. For an example, see
- :class:`collections.defaultdict`.
+ Return the item of *d* with key *key*. Raises a :exc:`KeyError` if *key*
+ is not in the map.
-.. describe:: d[key] = value
+ .. versionadded:: 2.5
+ If a subclass of dict defines a method :meth:`__missing__`, if the key
+ *key* is not present, the ``d[key]`` operation calls that method with
+ the key *key* as argument. The ``d[key]`` operation then returns or
+ raises whatever is returned or raised by the ``__missing__(key)`` call
+ if the key is not present. No other operations or methods invoke
+ :meth:`__missing__`. If :meth:`__missing__` is not defined,
+ :exc:`KeyError` is raised. :meth:`__missing__` must be a method; it
+ cannot be an instance variable. For an example, see
+ :class:`collections.defaultdict`.
- Set ``d[key]`` to *value*.
+ .. describe:: d[key] = value
-.. describe:: del d[key]
+ Set ``d[key]`` to *value*.
- Remove ``d[key]`` from *d*. Raises a :exc:`KeyError` if *key* is not in the
- map.
+ .. describe:: del d[key]
-.. describe:: key in d
+ Remove ``d[key]`` from *d*. Raises a :exc:`KeyError` if *key* is not in the
+ map.
- Return ``True`` if *d* has a key *key*, else ``False``.
+ .. describe:: key in d
- .. versionadded:: 2.2
+ Return ``True`` if *d* has a key *key*, else ``False``.
-.. describe:: key not in d
+ .. versionadded:: 2.2
- Equivalent to ``not key in d``.
+ .. describe:: key not in d
- .. versionadded:: 2.2
+ Equivalent to ``not key in d``.
-.. method:: dict.clear()
+ .. versionadded:: 2.2
- Remove all items from the dictionary.
+ .. method:: clear()
-.. method:: dict.copy()
+ Remove all items from the dictionary.
- Return a shallow copy of the dictionary.
+ .. method:: copy()
-.. method:: dict.fromkeys(seq[, value])
+ Return a shallow copy of the dictionary.
- Create a new dictionary with keys from *seq* and values set to *value*.
+ .. method:: fromkeys(seq[, value])
- :func:`fromkeys` is a class method that returns a new dictionary. *value*
- defaults to ``None``.
+ Create a new dictionary with keys from *seq* and values set to *value*.
- .. versionadded:: 2.3
+ :func:`fromkeys` is a class method that returns a new dictionary. *value*
+ defaults to ``None``.
-.. method:: dict.get(key[, default])
+ .. versionadded:: 2.3
- Return the value for *key* if *key* is in the dictionary, else *default*. If
- *default* is not given, it defaults to ``None``, so that this method never
- raises a :exc:`KeyError`.
+ .. method:: get(key[, default])
-.. method:: dict.has_key(key)
+ Return the value for *key* if *key* is in the dictionary, else *default*.
+ If *default* is not given, it defaults to ``None``, so that this method
+ never raises a :exc:`KeyError`.
- ``d.has_key(key)`` is equivalent to ``key in d``, but deprecated.
+ .. method:: has_key(key)
-.. method:: dict.items()
+ ``dict.has_key(key)`` is equivalent to ``key in d``, but deprecated.
- Return a copy of the dictionary's list of ``(key, value)`` pairs.
+ .. method:: items()
- .. note::
+ Return a copy of the dictionary's list of ``(key, value)`` pairs.
- Keys and values are listed in an arbitrary order which is non-random, varies
- across Python implementations, and depends on the dictionary's history of
- insertions and deletions. If :meth:`items`, :meth:`keys`, :meth:`values`,
- :meth:`iteritems`, :meth:`iterkeys`, and :meth:`itervalues` are called with no
- intervening modifications to the dictionary, the lists will directly correspond.
- This allows the creation of ``(value, key)`` pairs using :func:`zip`: ``pairs =
- zip(d.values(), d.keys())``. The same relationship holds for the
- :meth:`iterkeys` and :meth:`itervalues` methods: ``pairs = zip(d.itervalues(),
- d.iterkeys())`` provides the same value for ``pairs``. Another way to create the
- same list is ``pairs = [(v, k) for (k, v) in d.iteritems()]``.
+ .. note::
-.. method:: dict.iteritems()
+ Keys and values are listed in an arbitrary order which is non-random,
+ varies across Python implementations, and depends on the dictionary's
+ history of insertions and deletions. If :meth:`items`, :meth:`keys`,
+ :meth:`values`, :meth:`iteritems`, :meth:`iterkeys`, and
+ :meth:`itervalues` are called with no intervening modifications to the
+ dictionary, the lists will directly correspond. This allows the
+ creation of ``(value, key)`` pairs using :func:`zip`: ``pairs =
+ zip(d.values(), d.keys())``. The same relationship holds for the
+ :meth:`iterkeys` and :meth:`itervalues` methods: ``pairs =
+ zip(d.itervalues(), d.iterkeys())`` provides the same value for
+ ``pairs``. Another way to create the same list is ``pairs = [(v, k) for
+ (k, v) in d.iteritems()]``.
- Return an iterator over the dictionary's ``(key, value)`` pairs.
- See the note for :meth:`dict.items`.
+ .. method:: iteritems()
- .. versionadded:: 2.2
+ Return an iterator over the dictionary's ``(key, value)`` pairs. See the
+ note for :meth:`dict.items`.
-.. method:: dict.iterkeys()
+ .. versionadded:: 2.2
- Return an iterator over the dictionary's keys. See the note for
- :meth:`dict.items`.
+ .. method:: iterkeys()
- .. versionadded:: 2.2
+ Return an iterator over the dictionary's keys. See the note for
+ :meth:`dict.items`.
-.. method:: dict.itervalues()
+ .. versionadded:: 2.2
- Return an iterator over the dictionary's values. See the note for
- :meth:`dict.items`.
+ .. method:: itervalues()
- .. versionadded:: 2.2
+ Return an iterator over the dictionary's values. See the note for
+ :meth:`dict.items`.
-.. method:: dict.keys()
+ .. versionadded:: 2.2
- Return a copy of the dictionary's list of keys. See the note for
- :meth:`dict.items`.
+ .. method:: keys()
-.. method:: dict.pop(key[, default])
+ Return a copy of the dictionary's list of keys. See the note for
+ :meth:`dict.items`.
- If *key* is in the dictionary, remove it and return its value, else return
- *default*. If *default* is not given and *key* is not in the dictionary, a
- :exc:`KeyError` is raised.
+ .. method:: pop(key[, default])
- .. versionadded:: 2.3
+ If *key* is in the dictionary, remove it and return its value, else return
+ *default*. If *default* is not given and *key* is not in the dictionary,
+ a :exc:`KeyError` is raised.
-.. method:: dict.popitem()
+ .. versionadded:: 2.3
- Remove and return an arbitrary ``(key, value)`` pair from the dictionary.
+ .. method:: popitem()
- :func:`popitem` is useful to destructively iterate over a dictionary, as
- often used in set algorithms. If the dictionary is empty, calling
- :func:`popitem` raises a :exc:`KeyError`.
+ Remove and return an arbitrary ``(key, value)`` pair from the dictionary.
-.. method:: dict.setdefault(key[, default])
+ :func:`popitem` is useful to destructively iterate over a dictionary, as
+ often used in set algorithms. If the dictionary is empty, calling
+ :func:`popitem` raises a :exc:`KeyError`.
- If *key* is in the dictionary, return its value. If not, insert *key* with a
- value of *default* and return *default*. *default* defaults to ``None``.
+ .. method:: setdefault(key[, default])
-.. method:: dict.update([other])
+ If *key* is in the dictionary, return its value. If not, insert *key*
+ with a value of *default* and return *default*. *default* defaults to
+ ``None``.
- Update the dictionary with the key/value pairs from *other*, overwriting existing
- keys. Return ``None``.
+ .. method:: update([other])
- :func:`update` accepts either another dictionary object or an iterable of
- key/value pairs (as a tuple or other iterable of length two). If keyword
- arguments are specified, the dictionary is then is updated with those
- key/value pairs: ``d.update(red=1, blue=2)``.
+ Update the dictionary with the key/value pairs from *other*, overwriting
+ existing keys. Return ``None``.
- .. versionchanged:: 2.4
- Allowed the argument to be an iterable of key/value pairs and allowed
- keyword arguments.
+ :func:`update` accepts either another dictionary object or an iterable of
+ key/value pairs (as a tuple or other iterable of length two). If keyword
+ arguments are specified, the dictionary is then is updated with those
+ key/value pairs: ``d.update(red=1, blue=2)``.
+
+ .. versionchanged:: 2.4
+ Allowed the argument to be an iterable of key/value pairs and allowed
+ keyword arguments.
-.. method:: dict.values()
+ .. method:: values()
- Return a copy of the dictionary's list of values. See the note for
- :meth:`dict.items`.
+ Return a copy of the dictionary's list of values. See the note for
+ :meth:`dict.items`.
.. _bltin-file-objects:
projects / python / commitdiff