Python Set Union

In Python, a Set is an unordered, mutable, and unique collection of elements. Sets support basic set operations, including union, intersection, difference, and symmetric difference.

This article will provide a detailed introduction to Set union operations in Python, including how to use built-in methods and operators, along with some precautions and sample code. We hope that this article will help readers better understand and apply Set union operations.

1. Basic Concepts of Sets

Before introducing set unions, let’s review the basic concepts of sets.

A set is an unordered collection of elements. Each element must be unique within a set, meaning that duplicate elements are not allowed. Sets are mutable; elements can be added and removed.

In Python, sets are created using curly braces {} or the set() function. Below is some sample code that creates a set and demonstrates its basic properties.

# Create Set
set1 = {1, 2, 3, 4, 5}
set2 = set([2, 4, 6, 8])
set3 = set()

# Add element
set3.add(10)
set3.update([20, 30, 40])

# Delete element
set1.discard(3)
set2.remove(8)

# Print Set
print("Set 1:", set1)
print("Set 2:", set2)
print("Set 3:", set3)

Output:

Set 1: {1, 2, 4, 5}
Set 2: {2, 4, 6}
Set 3: {10, 40, 20, 30}

Through the above code examples, we created three Sets and demonstrated how to add and remove elements from them. The resulting output shows the elements in the Sets, and we can see that the Sets are unordered.

2. Set Union Operation

The Set union combines two or more Sets into a new Set. All elements in the new Set are the same as the elements in the original Sets, with no duplicates.

In Python, there are two ways to compute the union of Sets: using the union() method or the | operator. Below are example code for both methods.

2.1 Using the union() Method

The union() method is a built-in method of the Set class. It accepts one or more Sets as arguments and returns a new Set containing the union of all the elements in the Sets. The following is the sample code:

# Create a Set
set1 = {1, 2, 3}
set2 = {3, 4, 5}
set3 = {5, 6, 7}

# Calculate the union
union_set = set1.union(set2, set3)

# Print the result
print("Union:", union_set)

Output:

Union: {1, 2, 3, 4, 5, 6, 7}

2.2 Using the | Operator

| operator can be used to calculate the union of two sets, which yields the same result as using the union() method. Below is example code using the | operator:

# Create a Set
set1 = {1, 2, 3}
set2 = {3, 4, 5}
set3 = {5, 6, 7}

# Calculate the union
union_set = set1 | set2 | set3

# Print the result
print(“Union:”, union_set)

The output is the same as the previous example:

Union: {1, 2, 3, 4, 5, 6, 7}

<p>As you can see from the above code, you can easily calculate the union of two sets using either the union() method or the | operator. The choice between these two methods depends on personal preference and code readability. </p>
<h2>3. Union Operation Notes</h2>
<p>When using the Set union operation, please note the following:</p>
<ul>
<li>The result of the Set union operation is a new Set; the original Set remains unchanged.</li>
<li>The union operation removes duplicate elements to ensure that the result is unique.</li>
<li>The union operation is unordered; the order of the resulting set may differ from the order of the input Sets.</li>
<li>The union operation can accept multiple Sets as parameters and compute the union of multiple Sets.</li>
</ul>
<p>Based on the above considerations, you can flexibly apply the Set union operation in actual coding to meet specific needs.</p>
<h2>4. Example Code</h2>
<p>The following is a more complex example code that demonstrates how to use the Set union operation. First, we create three Sets, representing the students in the three classes:

<pre><code class="language-python line-numbers"># Create a list of students in the three classes
class1 = {"Alice", "Bob", "John", "Amy", "Kate"}
class2 = {"John", "Amy", "Tom", "Emma"}
class3 = {"Bob", "Kate", "Tom", "Jake"}

# Calculate the union
all_students = class1.union(class2, class3)

# Print the result
print("All students:", all_students)

After running the above code, the output is as follows:

All students: {'John', 'Jake', 'Kate', 'Bob', 'Tom', 'Alice', 'Amy', 'Emma'}

Through the above example code, we created student lists for three classes and calculated the union of all students. The resulting set contains the names of students from all classes, with no duplicate elements.

5. Summary

This article detailed the union operation of sets in Python. We learned the basic concepts and features of sets, as well as how to use the union() method and the | operator to calculate the union of sets. Additionally, some precautions regarding the union operation were highlighted, and example code was provided.

The union operation of sets is a commonly used operation in Python programming, allowing you to conveniently merge multiple sets and remove duplicate elements. By flexibly using the union operation of sets, we can more efficiently process various set data and meet practical programming needs.