Sequence Comparison¶

Python compares sequences (strings, lists, tuples) lexicographically — element by element from left to right.

String Comparison¶

Strings are compared character by character using ASCII/Unicode values.

print("apple" < "banana")   # True
print("apple" < "apricot")  # True (5th char: 'l' < 'r')
print("Apple" < "apple")    # True (uppercase comes first)

ASCII Order¶

Capital letters have lower ASCII values than lowercase:

print(ord('A'))  # 65
print(ord('Z'))  # 90
print(ord('a'))  # 97
print(ord('z'))  # 122

This means:

print("Zebra" < "apple")  # True (Z=90 < a=97)
print("Girl" < "boy")     # True (G=71 < b=98)

Caution: This differs from dictionary ordering where case is typically ignored.

List Comparison¶

Lists are compared element by element:

print([1, 2, 3] < [1, 2, 4])  # True (3 < 4)
print([1, 2, 3] < [1, 3, 0])  # True (2 < 3, rest ignored)
print([1, 2, 3] < [2, 0, 0])  # True (1 < 2, rest ignored)

First Difference Wins¶

print([0, 1, 2] < [5, 1, 2])          # True (0 < 5)
print([0, 1, 2000000] < [0, 1, 2])    # False (2000000 > 2)

String Elements¶

print(['Jones', 'Sally'] < ['Jones', 'Fred'])  # False ('S' > 'F')
print(['Jones', 'Sally'] < ['Adams', 'Sam'])   # False ('J' > 'A')

Tuple Comparison¶

Tuples follow the same rules as lists:

print((1, 2, 3) < (1, 2, 4))  # True
print((1, 2, 3) < (1, 3, 0))  # True
print((0, 1, 2) < (5, 1, 2))  # True

Comparison Algorithm¶

Compare first elements
If equal, compare second elements
Continue until a difference is found or one sequence ends
Shorter sequence is "less than" if all compared elements are equal

print([1, 2] < [1, 2, 3])     # True (shorter)
print("ab" < "abc")           # True (shorter)
print((1, 2) == (1, 2))       # True (all equal)

Chained Comparisons¶

Python supports chained comparisons:

print(1 < 2 < 3)              # True (1<2 and 2<3)
print("a" < "b" < "c")        # True
print(1 < 2 < 3 < 4 < 5)      # True

This is equivalent to:

print(1 < 2 and 2 < 3)        # True

Mixed Type Comparison¶

Comparing incompatible types raises TypeError:

# Python 3
print([1, 2] < "ab")  # TypeError: '<' not supported
print((1, 2) < [1, 2])  # TypeError

Practical Use: Sorting¶

Lexicographic comparison enables natural sorting:

names = ["Charlie", "Alice", "Bob"]
print(sorted(names))  # ['Alice', 'Bob', 'Charlie']

# Tuples sort by first element, then second
records = [("Bob", 25), ("Alice", 30), ("Bob", 20)]
print(sorted(records))  # [('Alice', 30), ('Bob', 20), ('Bob', 25)]

Summary¶

Sequence	Comparison Basis
String	Character ASCII/Unicode values
List	Element-by-element comparison
Tuple	Element-by-element comparison

Comparison stops at first difference
Shorter sequence is "less than" if prefixes match
Case matters: 'A' < 'a' (ASCII order)