บทนำสู่เซต

เซตคืออะไร

การสร้างเซต

# Creates a set of fruits using curly braces
fruits = {"apple", "banana", "cherry"}

# Creates a set of numbers using the set() function
numbers = set([1, 2, 3, 4, 5])

การเข้าถึงรายการในเซต

# Iterates through each fruit in the set and prints it
for fruit in fruits:
    print(fruit)

การเพิ่มรายการลงในเซต

# Adds a new fruit to the set
fruits.add("orange")

# Attempts to add a duplicate fruit (will have no effect)
fruits.add("apple")

# Prints the updated set
print(fruits)  # Output might vary due to unordered nature

การนำรายการออกจากเซต

# Removes 'banana' from the set
fruits.remove("banana")

# Removes 'grape' if it exists; does nothing otherwise
fruits.discard("grape")

# Prints the updated set
print(fruits)  # Output might vary

การดำเนินการกับเซต

# Creates two sets of numbers
set_a = {1, 2, 3, 4}
set_b = {3, 4, 5, 6}

# Union of set_a and set_b
union_set = set_a.union(set_b)
print("Union:", union_set)  # Output: {1, 2, 3, 4, 5, 6}

# Intersection of set_a and set_b
intersection_set = set_a.intersection(set_b)
print("Intersection:", intersection_set)  # Output: {3, 4}

# Difference of set_a from set_b
difference_set = set_a.difference(set_b)
print("Difference:", difference_set)  # Output: {1, 2}

โปรแกรมตัวอย่าง: ผู้เข้าชมที่ไม่ซ้ำกัน

# Initializes an empty set to store unique visitor names
unique_visitors = set()

# List of visitors (including duplicates)
visitors = ["Alice", "Bob", "Charlie", "Alice", "Diana", "Bob"]

# Adds each visitor to the set
for visitor in visitors:
    unique_visitors.add(visitor)  # Adds the visitor name to the set

# Prints the total number of unique visitors
print("Total Unique Visitors:", len(unique_visitors))  # Output: 4

# Prints the names of unique visitors
print("Unique Visitors:", unique_visitors)  # Output: {'Alice', 'Bob', 'Charlie', 'Diana'}

# Creates a set of numbers
numbers = {1, 2, 3, 4, 4, 5}

# Adds a new number to the set
numbers.add(6)

# Attempts to add a duplicate number
numbers.add(2)

# Prints the set
print(numbers)

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