adding ranges in python

Question

I have the following code:

for inc in range(0, ninc+1)+range(ninc-1,-1,-1):

But it gives me such an error:

for inc in range(0, ninc+1)+range(ninc-1,-1,-1):
TypeError: unsupported operand type(s) for +: 'range' and 'range'

I am using Python 3.3.2. Any suggestions?

What Python version are you using? – Christian Tapia Dec 29 '13 at 15:30 — Christian Tapia, Dec 29 '13 at 15:30
What exactly are you expecting the result to be, and why? – Karl Knechtel Dec 29 '13 at 16:02 — Karl Knechtel, Dec 29 '13 at 16:02

score 5 · Answer 1 · answered Dec 29 '13 at 15:33

5

range objects aren't lists, so you can't add them together. You can, however, chain the two iterables:

import itertools

for inc in itertools.chain(range(0, ninc + 1), range(ninc - 1, -1, -1)):
    ...

answered Dec 29 '13 at 15:33

Blender

thefourtheye · Answer 2 · 2013-12-29T17:19:07.007

2

Python 3.x's range doesn't return a list, but a range object. So, we have to create a list out of that object like this

rlist = list(range(0, ninc+1))
for inc in rlist + rlist[-2::-1]:

edited Dec 29 '13 at 17:19

answered Dec 29 '13 at 15:30

thefourtheye

The second list is the reversal of the first, so you'll build 2 lists, when one will be enogh – volcano Dec 29 '13 at 17:15
@volcano You are absolutely correct :) Please check my updated answer now. – thefourtheye Dec 29 '13 at 17:19

score 2 · Answer 3 · edited May 23 '17 at 10:25

2

Use itertools.chain:

from itertools import chain
myIterator = chain(range(0, ninc + 1), range(ninc - 1, -1, -1))
for x in myIterator:
..

or something similar.

edited May 23 '17 at 10:25

Community

answered Dec 29 '13 at 15:34

Joel R

Cameron White · Answer 4 · 2013-12-29T17:02:39.380

0

Maybe range.extend (python2 only)

range_1 = range(2)
range_2 = range(3)
range_1.extend(range_2)

print(range_1)
[0, 1, 0, 1, 2]

edited Dec 29 '13 at 17:02

answered Dec 29 '13 at 16:54

Cameron White

This won't work in Python 3; there is no `range.extend`, there's only `list.extend`, and in Python 3 `range` doesn't return a `list`. – DSM Dec 29 '13 at 16:59

4 Answers4