[issue47257] add methods to get first and last elements of a range

[paul rubin]

paul rubin  added the comment:

Oh nice, I didn't realize you could do that.  len(range) and bool(range) (to 
test for empty) also work.  Ok I guess this enhancement is not needed.  I will 
close ticket, hope that is procedurally correct, otherwise feel free to fix.  
Thanks.

--
resolution:  -> rejected
stage:  -> resolved
status: open -> closed

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue47257] add methods to get first and last elements of a range

[Mark Dickinson]

Mark Dickinson  added the comment:

> but it's messy and potentially tricky to get the actual first and last values 
> of the range

Doesn't simple indexing already provide what you need here?

>>> range(1, 5, 2)[0]  # first element of range
1
>>> range(1, 5, 2)[-1]  # last element of range
3

--
nosy: +mark.dickinson

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue47257] add methods to get first and last elements of a range

[paul rubin]

New submission from paul rubin :

Inspired by a question on comp.lang.python about how to deal with an int set 
composed of integers and ranges.  Range objects like range(1,5,2) contain 
start, stop, and step values, but it's messy and potentially tricky to get the 
actual first and last values of the range.  Examples:

range(1,5,2) - first = 1, last = 3

range (5, 1, 2) - range is empty, first = last = None

range(5, 1, -1) - first is 5, last is 2

Note in the case where the range is not empty, you can get the "last" by a 
messy calculation but it's easier to pick the first element from the reverse 
iterator.  But then you might forget to catch the stopiteration exception in 
the case that the list is empty.  The same goes for the first element, roughly. 
 And constructing the iterators just to pick one element seems like unnecessary 
overhead.

So it is better to have actual methods for these, with type Optional[int].  
Then mypy should remind you to check for the empty case if you forget.

--
messages: 416962
nosy: phr
priority: normal
severity: normal
status: open
title: add methods to get first and last elements of a range
type: enhancement

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com