Python set() Function
Python3 Built-in Functionsset()It is a built-in function in Python used to create a mutable set.
A set is an unordered collection of unique elements, similar to the concept of a set in mathematics.set()The function can create a set from other iterable objects, commonly used for deduplication, set operations, and other scenarios.
Word Definition： setMeans "set", an unordered collection of unique elements in Python.
Basic Syntax and Parameters
Syntax Format
set(iterable)
Parameter Description
- Parameter iterable：
- Type: Iterable object
- Description: The iterable object to be converted into a set.
Function Description
- Return Value: Returns a mutable set.
- Special Value: Returns an empty set if no argument is passed.
set()(Note:{}an empty dictionary is created).
Examples
Example 1: Create a Set
Examples
# Create from a list (automatically deduplicates)
lst = [1, 2, 2, 3, 3, 3, 4]
s = set(lst)
print(s) # Output: {1, 2, 3, 4}
# Create from a string
s = set("hello")
print(s) # Output: {'h', 'e', 'l', 'o'}
# Create from a tuple
t = (1, 2, 3, 2, 1)
s = set(t)
print(s) # Output: {1, 2, 3}
# Create from a dictionary (keys only)
d = {"a": 1, "b": 2, "c": 3}
s = set(d)
print(s) # Output: {'a', 'b', 'c'}
# Empty set
s = set()
print(s) # Output: set()
print(type(s)) # Output: <class 'set'>
lst = [1, 2, 2, 3, 3, 3, 4]
s = set(lst)
print(s) # Output: {1, 2, 3, 4}
# Create from a string
s = set("hello")
print(s) # Output: {'h', 'e', 'l', 'o'}
# Create from a tuple
t = (1, 2, 3, 2, 1)
s = set(t)
print(s) # Output: {1, 2, 3}
# Create from a dictionary (keys only)
d = {"a": 1, "b": 2, "c": 3}
s = set(d)
print(s) # Output: {'a', 'b', 'c'}
# Empty set
s = set()
print(s) # Output: set()
print(type(s)) # Output: <class 'set'>
Expected output:
{1, 2, 3, 4}
{'h', 'e', 'l', 'o'}
{1, 2, 3}
{'a', 'b', 'c'}
set()
<class 'set'>
Code analysis:
- Sets automatically remove duplicate elements.
- Sets are unordered; the order of elements may vary.
- Note:
{}An empty dictionary is created, not an empty set.
Example 2: Set Operations
Examples
# Create two sets
A = {1, 2, 3, 4}
B = {3, 4, 5, 6}
# Union
print(A | B) # Output: {1, 2, 3, 4, 5, 6}
print(A.union(B)) # Output: {1, 2, 3, 4, 5, 6}
# Intersection
print(A & B) # Output: {3, 4}
print(A.intersection(B)) # Output: {3, 4}
# Difference (A - B)
print(A - B) # Output: {1, 2}
print(A.difference(B)) # Output: {1, 2}
# Symmetric difference
print(A ^ B) # Output: {1, 2, 5, 6}
print(A.symmetric_difference(B)) # Output: {1, 2, 5, 6}
A = {1, 2, 3, 4}
B = {3, 4, 5, 6}
# Union
print(A | B) # Output: {1, 2, 3, 4, 5, 6}
print(A.union(B)) # Output: {1, 2, 3, 4, 5, 6}
# Intersection
print(A & B) # Output: {3, 4}
print(A.intersection(B)) # Output: {3, 4}
# Difference (A - B)
print(A - B) # Output: {1, 2}
print(A.difference(B)) # Output: {1, 2}
# Symmetric difference
print(A ^ B) # Output: {1, 2, 5, 6}
print(A.symmetric_difference(B)) # Output: {1, 2, 5, 6}
Expected output:
{1, 2, 3, 4, 5, 6}
{1, 2, 3, 4, 5, 6}
{3, 4}
{3, 4}
{1, 2}
{1, 2}
{1, 2, 5, 6}
{1, 2, 5, 6}
Sets support rich set operations: union, intersection, difference, and symmetric difference.
Other Extensions