Python (1..n) syntax?

Question

I see in the code on this Sage wiki page the following code:

@interact
def _(order=(1..12)):

Is this (1..n) syntax unique to Sage or is it something in Python? Also, what does it do?

Answer 1

(1..n) syntax does not exist in Python.

Answer 2

This is not Python syntax. I would guess that it creates a range from 1 to 12.

Answer 3

It's Sage-specific. You can use preparse to see how it is desugared to:

sage: preparse("(1..12)")
'(ellipsis_iter(Integer(1),Ellipsis,Integer(12)))'

See here for documentation of ellipsis_iter, here for information on the preparser.

Answer 4

There was a Python PEP to add this notation to Python, but it was rejected. Robert Bradshaw decided to implement it anyways, but for the Sage preparser. He implemented the following:

• (a..b) -- like xrange, so an iterator

• [a..b] -- list, including endpoints

• [a,b,..,c] -- arithmetic progression