range exits loop without action when start is higher than end

[AsaDawson]

BPO	13480
Nosy	@bitdancer

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2011-11-25.14:59:31.186>
created_at = <Date 2011-11-25.14:51:34.915>
labels = ['type-bug', 'invalid']
title = 'range exits loop without action when start is higher than end'
updated_at = <Date 2011-11-25.14:59:31.177>
user = 'https://bugs.python.org/AsaDawson'

bugs.python.org fields:

activity = <Date 2011-11-25.14:59:31.177>
actor = 'r.david.murray'
assignee = 'none'
closed = True
closed_date = <Date 2011-11-25.14:59:31.186>
closer = 'r.david.murray'
components = ['None']
creation = <Date 2011-11-25.14:51:34.915>
creator = 'Asa.Dawson'
dependencies = []
files = []
hgrepos = []
issue_num = 13480
keywords = []
message_count = 2.0
messages = ['148315', '148316']
nosy_count = 2.0
nosy_names = ['r.david.murray', 'Asa.Dawson']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue13480'
versions = ['Python 2.7', 'Python 3.2']

[AsaDawson]

range has an odd behavior in which it assumes (regardless of start/end) that it should be counting up. Attempting something such as:

for i in range(10,0):
    print i

This loop simply runs through without doing anything, because start is larger than end.

I'm putting forward the proposition that when end is lower than start, range should count downwards rather than upwards.

[bitdancer]

Nope. If you want to count backward, use a negative step. Not doing anything if end is lower than start allows code to take advantage of "don't care" edge cases, just like 'abc'[4:] returning the empty string does. Range is often used in 'for' loops, so having the loop not execute if the computed end is less than the computed start is an intentional and important feature.