In Python programming, a Set is an unordered collection data type that is iterable, mutable and contains no duplicate elements. It is one of the most optimized methods to check whether an element exists in a particular field or not. A frozenset in Python is similar to a set, except that frozenset elements are immutable. It means that they cannot be changed later once generated.
In this blog, we will look at fronzenset in Python in detail with the help of some examples.
What is frozenset in Python?
The frozenset is an inbuild function in Python. It takes an iterable object as an argument and returns its frozenset object initialized with the arguments from the given iterable. It is similar to sets in Python except for the mutable nature. The elements from the frozenset cannot be removed or added later.
The frozenset accepts any iterable object as an argument and transforms it into an immutable object. The order or elements are not retained whenever passed to the frozenset function.
Syntax of Frozenset in Python
frozenset(<iterable_object>)
Parameters of Frozenset in Python
The frozenset() function only takes a single argument which is an Iterable. This function takes an iterable object as input which contains the list of elements to initialize the frozenset. The iterable can be a dictionary, set, tuple, etc.
Note: This argument is optional.
Return Value of Frozenset in Python
The frozenset() function returns a frozenset object with given values. An empty frozenset object is returned when no arguments are passed.
Examples of Frozenset in Python
Let's now see several examples of frozenset in different scenarios:
Empty Frozenset
If no parameters are passed to the frozenset() function, the function returns an empty frozenset object.
Example
Python
Python
# Creating a tuple of numbers numbers = (1, 2, 3, 4, 5)
# Creating an empty frozenset fSet_empty = frozenset() print('The empty frozen set is:', fSet_empty)
# Creating another frozenset with some elements fset_obj = frozenset(numbers); print('The frozen set of tuple is: ', fset_obj)
Output
Explanation
From the above example of frozenset in Python, the fSet_empty is created with no parameter, which results in an empty frozenset object.
Item Assignment in Frozenset
Frozenset object is immutable in nature. Therefore we cannot add or change elements using frozenset() function.
Example
Python
Python
# Creating a list courses = ["Web development", "Machine Learning"]
# Creating a frozenset f_obj = frozenset(courses)
# Changing an element of frozenset f_obj[1] = "Data Science"
Output
Explanation
From the above example of frozenset in Python, we can see that frozenset objects are not changeable. If we try to make a change in it, an error message will appear, suggesting that item assignment is not possible.
Frozenset and Dictionaries
Till now, we have created frozenset from lists and tuples. Since the frozenset objects are immutable in nature, they are mainly used in dictionaries as keys.
Example
Python
Python
# Initializing an empty frozenset object frozenset_Obj = frozenset()
# Printing the frozenset print("Empty Frozenset object is :", frozenset_Obj) print()
# Generating some elements Student = {"name": "Aalia", "marks": 100}
# Initializing the frozenset with some elements Student = frozenset(Student) print("Non-Empty Frozenset object is :") print(Student)
Output
Explanation
In the above code of frozenset in Python, we were able to create a non-empty frozenset object of dictionaries using the frozenset() function.
Note: The order in which the elements are passed in the frozenset() function need not be the same as the returned frozenset object.
Frozenset Operations
Now, let's talk about some of the operations that can be done on frozensets. We can perform operations like copy, union, intersection, difference, and symmetric difference.
Example
Python
Python
# Frozensets A = frozenset([1, 2, 4, 6, 3, 8]) B = frozenset([2, 4, 6, 3, 1, 7])
# Copying a frozenset C = A.copy() print('Copy of frozenset:', C) print()
# Difference of frozenset print('Difference of frozenset:', A.difference(B)) print()
# Union of frozenset print('Union of frozenset:', A.union(B)) print()
# Intersection of frozenset print('Intersection of frozenset:', A.intersection(B)) print()
# Symmetric difference of frozenset print('Symmetric difference of frozenset:', A.symmetric_difference(B))
Output
Explanation
In the above example of frozenset in Python, we can see that copy(), union(), and intersection() methods are giving the expected results as their names suggest. Now the difference() method doesn’t give the element-wise difference. Rather, it gives the elements which are in frozenset A only and are not common between A and B.
Furthermore, the symmetric_difference() method works opposite to the difference method. It gives the elements that are not common between A and B and are unique in A and B.
The frozenset in Python has some other build methods like issubset(), isdisjoint(), and issuperset(). These methods are useful in many set operations.
Example
Python
Python
# Frozensets A = frozenset(['u', 'v', 'w', 'x']) B = frozenset(['b', 'c', 'd', 'e']) C = frozenset(['d', 'e'])
# isdisjoint() method print("Check if A and C are disjoint sets: ", A.isdisjoint(C))
# issubset() method print("Check if C is subset of B: ", C.issubset(B))
# issuperset() method print("Check if B is superset of C: ", B.issuperset(C))
Output
Explanation
In the above example of a frozenset in Python, the isdisjoint() function verifies whether the frozenset A is a disjoint set of B. If it is, then we will get a boolean value True otherwise False. Similarly, the issubset() and issuperset() functions are working in the same manner.
Python's frozenset() method is used to create an immutable frozenset object from an iterable of elements. It raises two types of exceptions:
TypeError: If the iterable passed to frozenset() contains any mutable objects, it will raise a TypeError exception. This is because frozensets are immutable, and mutable objects cannot be members of frozensets
ValueError: If the iterable passed to frozenset() contains any duplicate elements, it will raise a ValueError exception. This is because frozensets cannot contain duplicate elements
Frequently Asked Questions
What is a frozenset in Python?
The frozenset is an inbuild function in Python. It takes an iterable object as an argument and returns its frozenset object initialized with the arguments from the given iterable.
What is a FrozenList?
A FrozenList is an immutable list in Python, meaning its elements cannot be modified after creation.
Can we store Frozenset in a list in Python?
Yes, you can store a Frozenset in a list in Python. Lists can hold any data type, including Frozensets, which are immutable.
What is the difference between a frozenset and a tuple?
Tuple and frozenset are both immutable data types in nature. But a frozenset is a set of elements, while a tuple is a list of elements.
What is the difference between set and frozenset in Python?
The main difference is that a set is mutable; it can be modified later in the program. Whereas a frozenset is immutable, we cannot alter it after its creation, and changing it will result in TypeError.
Which method takes extra memory, a set or a frozenset?
Frozenset takes less memory compared to a regular set in Python. That is because frozensets are immutable and can be hashed and used in dictionaries as unique keys.
When to use a frozenset in Python?
When you require a collection of distinct items that cannot be changed once they are formed, you should use a frozenset. These can be helpful whenever we want a set to remain as it is throughout the program.
Conclusion
This article discusses the frozenset in Python along with different examples and operations. We hope this blog has helped you enhance your knowledge of frozenset in Python. If you want to learn more, then check out our articles.
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