how to understand `3

Question

I am not sure where to find the reference to explain the following

>>> 3<range(3)
True
>>> [1,2]<range(3)
False
>>> [1]<range(3)
False
>>> [4]<range(3)
False
>>> [4,1,2,3]<range(3)
False

Thank you!

@MartijnPieters, are each of the elements not evaluated at corresponding indexes? — Padraic Cunningham, Aug 27 '14 at 17:30
@PadraicCunningham: `range()` produces a list, starting with `0`. — Martijn Pieters, Aug 27 '14 at 17:30
@PadraicCunningham: for list yes, but when types are different they are ordered by type name — brain storm, Aug 27 '14 at 17:31
@brainstorm: I momentarily overlooked that `range()` produces a list too, but it starts with `0`. So the second test is equivalent to `[1, 2] < [0, 1, 2]`, and lists are ordered lexicographically. — Martijn Pieters, Aug 27 '14 at 17:32
@MartijnPieters. that is what I am asking, if the last example you change the third element to 1 the result would be True — Padraic Cunningham, Aug 27 '14 at 17:32
@PadraicCunningham: what last example? In the question, or in the comments? In the question, the first element is 4, which is not smaller than 0, so the test is `False`. — Martijn Pieters, Aug 27 '14 at 17:38

score 3 · Accepted Answer · edited May 23 '17 at 12:05

In Python 2, range() produces a list object. The first test compares two different types, at which point numbers always come before other types:

>>> range(3)
[0, 1, 2]
>>> 3 < []
True

The rest is just comparing lists against [0, 1, 2]; lists are compared lexicographically and 0 is lower than any of the first values in all your other tests.

Your initial value should be lower than 0:

>>> [-1] < range(3)
True

or, if it is equal, the next value should be lower than 1:

>>> [0, 0] < range(3)
True

etc.

See the Comparisons section of the expressions documentation:

Tuples and lists are compared lexicographically using comparison of corresponding elements. This means that to compare equal, each element must compare equal and the two sequences must be of the same type and have the same length.

how to understand `3

1 Answers1