เซต (set) ใน Python

# A set stores unique values with no fixed order.
tags = {"python", "code", "python", "learn"}
print(len(tags))                 # the duplicate "python" is kept once
print("code" in tags)            # fast membership test

tags.add("fun")
tags.discard("code")
print(sorted(tags))

# Remove duplicates from a list.
numbers = [3, 1, 3, 2, 1]
print(sorted(set(numbers)))

# Set operations.
a = {1, 2, 3, 4}
b = {3, 4, 5}
print(a | b)   # union: in either set
print(a & b)   # intersection: in both
print(a - b)   # difference: in a but not in b