Python also provides a lot of built-in methods to manipulate sets, we will learn these methods later. The statement x &= s is effectively equivalent to x = x & s. It isn’t modifying the original x. Complaints and insults generally won’t make the cut here. There is no corresponding method. Frozenset is a built-in type that has the characteristics of a set, but unlike set, frozenset is immutable, its elements cannot be changed once assigned. A Python list can be seen as a collection of values. Grouping objects into a set can be useful in programming as well, and Python provides a built-in set type to do so. For example: In Python, a set is an unordered sequence of elements, and each element is unique and must be immutable (which cannot be changed). Let’s see what all that means, and how you can work with sets in Python. The method is invoked on one of the sets, and the other is passed as an argument: The way they are used in the examples above, the operator and method behave identically. x1.update(x2) and x1 |= x2 add to x1 any elements in x2 that x1 does not already have: x1.intersection_update(x2) and x1 &= x2 update x1, retaining only elements found in both x1 and x2: x1.difference_update(x2) and x1 -= x2 update x1, removing elements found in x2: x1.symmetric_difference_update(x2) and x1 ^= x2 update x1, retaining elements found in either x1 or x2, but not both: Aside from the augmented operators above, Python supports several additional methods that modify sets. As we know, the elements in sets must be immutable. Our second step is to set the base case. The union() method or | operator in python can combine many sets(set1, set2, ...) into a single set. A set x1 is considered a proper subset of another set x2 if every element of x1 is in x2, and x1 and x2 are not equal. First, you can define a set with the built-in set() function: In this case, the argument is an iterable—again, for the moment, think list or tuple—that generates the list of objects to be included in the set. So we can create a mixed set as follows: There is a small trap when creating an empty set. Python’s built-in set type has the following characteristics: Sets are unordered. x1.union(x2) and x1 | x2 both return the set of all elements in either x1 or x2: More than two sets may be specified with either the operator or the method: The resulting set contains all elements that are present in any of the specified sets. However, the set itself is mutable. Simply put, the set is "a bunch of certain elements". The output of the above two methods is as follows: You will notice that the duplicate element "red" was removed after the set was created. As with the earlier tutorials on lists and dictionaries, when you are finished with this tutorial, you should have a good feel for when a set is an appropriate choice. x1.symmetric_difference(x2) and x1 ^ x2 return the set of all elements in either x1 or x2, but not both: The ^ operator also allows more than two sets: As with the difference operator, when multiple sets are specified, the operation is performed from left to right. In the following example we have three set numbers and we are checking whether they are subset of each other using issubset() method. unsupported operand type(s) for |: 'set' and 'tuple', symmetric_difference() takes exactly one argument (2 given), {'qux', 'corge', 'garply', 'foo', 'bar', 'baz'}, 'frozenset' object has no attribute 'add', 'frozenset' object has no attribute 'pop', 'frozenset' object has no attribute 'clear', {frozenset({'bar'}), frozenset({'baz'}), frozenset({'foo'})}, {frozenset({1, 2, 3}): 'foo', frozenset({'c', 'a', 'b'}): 'bar'}, Augmented Assignment Operators and Methods. However, the set itself is mutable. And the duplicate elements are automatically removed. This method returns true or false based on the comparison, if the calling set is a subset of the set passed as a parameter then this method returns true else it returns false. However, Python provides a whole host of operations on set objects that generally mimic the operations that are defined for mathematical sets. A class is an example of encapsulation as it encapsulates all the data that is member functions, variables, etc. It has been reassigned, not modified in place. A set x1 is considered a proper superset of another set x2 if x1 contains every element of x2, and x1 and x2 are not equal.


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