How Does Python Compare Lists with Greater Than and Less Than Operators?

Comparing Lists with the Greater Than or Less Than Operator: Lexicographical Ordering Unsurprises

Upon encountering code comparing lists directly using the greater than or less than operator (> and

To unravel this mystery, we turn to Python's documentation on Comparing Sequences and Other Types. It states that such comparisons follow lexicographical ordering, not element-by-element comparisons:

• The first two elements of the lists are compared. If they differ, this determines the outcome.
• If the first elements are equal, the next two elements are compared.
• This process continues until one list runs out of elements.

Consider the following example:

a = [3, 3, 3, 3]
b = [4, 4, 4, 4]

Since the first elements (3 and 4) differ, b is considered greater than a. This aligns with our assumption that all elements in b are greater than those in a.

However, the following case illustrates the lexicographical ordering rule more clearly:

a = [1, 1, 3, 1]
b = [1, 3, 1, 1]

Since the first elements (1) are equal, the comparison moves on to the next elements. In this case, the second element of a (1) is less than the second element of b (3). Therefore, despite the fact that a has more elements greater than 1 than b does, b is considered greater than a.

In summary, when comparing lists using the greater than or less than operator, Python employs lexicographical ordering, rather than element-by-element comparisons. This can lead to unexpected results, especially when lists contain elements of different values.

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