# [Tutor] Fwd: Re: Doubt in Python

Steven D'Aprano steve at pearwood.info
Thu Jan 17 10:28:12 EST 2019

```On Thu, Jan 17, 2019 at 09:57:03AM +0000, Alan Gauld via Tutor wrote:

> The algorithm is probably described somewhere in the documentation
> but my understanding is that it looks something like this(in pdeudo code):

List, tuple and string comparisons are defined as lexicographical order:

http://docs.python.org/tutorial/datastructures.html#comparing-sequences-and-other-types

https://en.wikipedia.org/wiki/Lexicographical_order

That's a fancy way of saying "dictionary order". That means that lists
are ordered in the same way that words are ordered in the dictionary:

- match up letters in the word (items in the list) in pairs;

- so long as the pairs of letters (items) are equal, keep going;

- as soon as you hit a pair that aren't equal, the order of that pair
determines the order of the words (lists);

- if one word runs out of letters (list runs out of items), then it
comes first;

- if all the pairs are equal, the words (lists) are equal.

Some examples:

[0, 1, 2] < [1, 2, 3] because 0 < 1

[0, 1, 2] < [0, 1, 2, 3] because the first three items are equal
but the first list is shorter.

[0, 1, 2, 3, 4, 5] < [0, 1, 999] because 2 < 999

[0, 999, 999, 999] < [1, 2] because 0 < 1

--
Steve
```