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# python tutorial - Python Set | Sets in Python - learn python - python programming

Learn Python - Python tutorial - python sets - Python examples - Python programs

A Set is an unordered collection data type that is iterable, mutable, and has no duplicate elements. Python’s set class represents the mathematical notion of a set. The major advantage of using a set, as opposed to a list, is that it has a highly optimized method for checking whether a speci?c element is contained in the set. This is based on a data structure known as a hash table.

Frozen Sets Frozen sets are immutable objects that only support methods and operators that produce a result without a?ecting the frozen set or sets to which they are applied.

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Methods for Sets

1. add(x) Method: Adds the item x to set if it is not already present in the set.

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-> This will add Daxit in people set.

2. union(s) Method: Returns a union of two set.Using the ‘|’ operator between 2 sets is the same as writing set1.union(set2)

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OR

-> Set population set will have components of both people and vampire

3. intersect(s) Method: Returns an intersection of two sets.The ‘&’ operator comes can also be used in this case.

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-> Set victims will contain the common element of people and vampire

4. difference(s) Method: Returns a set containing all the elements of invoking set but not of the second set. We can use ‘-‘ operator here.

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-> Set safe  will have all the elements that are in people but not vampire
5. clear() Method: Empties the whole set.

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-> Clears victim set

However there are two major pitfalls in Python sets:

1. The set doesn’t maintain elements in any particular order.
2. Only instances of immutable types can be added to a Python set.

Operators for Sets

Sets and frozen sets support the following operators:

key in s       # containment check

key not in s   # non-containment check

s1 == s2       # s1 is equivalent to s2

s1 != s2       # s1 is not equivalent to s2

s1 <= s2    # s1is subset of s2

s1 < s2     # s1 is proper subset of s2

s1 >= s2    # s1is superset of s2

s1 > s2     # s1 is proper superset of s2

s1 | s2        # the union of s1 and s2

s1 & s2 # the intersection of s1 and s2

s1 – s2        # the set of elements in s1 but not s2

s1 ˆ s2        # the set of elements in precisely one of s1 or s2

Code Snippet to illustrate all Set operations in Python

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