![]() Methods check an element for hashability and, if not, check for a Methods which need to hash an element to check for membership in a set. Instance of ImmutableSet, it is possible to construct sets of sets.Ī similar mechanism is needed by the _contains_() and remove() Since Set objects have a _as_immutable_() method returning an ![]() Method which returns an immutable equivalent. Hashable, the element is checked to see if it has an _as_immutable_() The mechanism is to always add a hashable element, or if it is not Objects are automatically copied to an ImmutableSet before being added Sets can only contain immutable elements. Protocol for automatic conversion to immutable ¶ discard ( 'Susan' ) # unconditionally remove element. issuperset ( engineers ) True > for group in. update ( engineers ) # update from another set > employees. issuperset ( engineers ) # superset test False > employees. add ( 'Marvin' ) # add element > print engineers Set() > employees. > from sets import Set > engineers = Set () > programmers = Set () > managers = Set () > employees = engineers | programmers | managers # union > engineering_management = engineers & managers # intersection > fulltime_management = managers - engineers - programmers # difference > engineers. Note, the non-operator versions of update(), intersection_update(),ĭifference_update(), and symmetric_difference_update() will accept The following table lists operations available in Set but not found in The following table lists operations available in ImmutableSet but not The list.sort() method is undefined for lists of sets. Since sets only define partial ordering (subset relationships), the output of Accordingly, sets do not implement the _cmp_() method. Of each other, so all of the following return False: ab. For example, any two disjoint sets are not equal and are not subsets The subset and equality comparisons do not generalize to a complete orderingįunction. If the first set is a proper superset of the second set (is a superset, but is ![]() A set is greater than another set if and only A set is less thanĪnother set if and only if the first set is a proper subset of the second set Two sets are equal if and only if every element of each set isĬontained in the other (each is a subset of the other). In addition, both Set and ImmutableSet support set to setĬomparisons. Set('abc') & 'cbs' in favor of the more readableĬhanged in version 2.3.1: Formerly all arguments were required to be sets. This precludes error-prone constructions like In contrast, their operator based counterparts require theirĪrguments to be sets. Note, the non-operator versions of union(), intersection(),ĭifference(), and symmetric_difference() will accept any iterable asĪn argument. Instances of Set and ImmutableSet both provide the following Objects do not have methods for adding or removing elements, so all of theĮlements must be known when the constructor is called. Immutable using the protocol described in section Protocol for automatic conversion to immutable.īecause ImmutableSet objects provide a _hash_() method, theyĬan be used as set elements or as dictionary keys. ImmutableSet ( ) ¶Ĭonstructs a new empty ImmutableSet object. Immutable using the protocol described in section Protocol for automatic conversion to immutable. Parameter is supplied, updates the set with elements obtained from iteration.Īll of the elements in iterable should be immutable or be transformable to an Set ( ) ¶Ĭonstructs a new empty Set object. For convenience in implementing sets of sets, inner setsĪre automatically converted to immutable form, for example, They can contain immutable collections such as tuples or instances of Sets cannot contain mutable elements such as lists or dictionaries. That the element defines both _eq_() and _hash_(). Requirements for set elements are the same as those for dictionary keys namely, The set classes are implemented using dictionaries. Something is a set: isinstance(obj, BaseSet). Both Set and ImmutableSetĭerive from BaseSet, an abstract class useful for determining whether ![]() The ImmutableSet class adds a _hash_() method but omits methods For advanced applications requiring a hash method, Most set applications use the Set class which provides every set methodĮxcept for _hash_(). Accordingly, sets do not support indexing, slicing, or Being an unordered collection, sets do not record element position or Like other collections, sets support x in set, len(set), and for x in set. Operations on sets such as intersection, union, difference, and symmetric Testing, removing duplicates from a sequence, and computing standard math Unordered collections of unique elements. The sets module provides classes for constructing and manipulating Deprecated since version 2.6: The built-in set/ frozenset types replace this module.
0 Comments
Leave a Reply. |