How to properly iterate over intervals in Python?

Question

I am quite new to Python (I'm more used to C, C#). I am trying to learn and I want to try to do things as 'Pythonic' as possible.

I want to iterate over intervals and then do something based on whether or not a number is in the interval. I know I can create my intervals using numpy.arrange (or some other array defintion) and then iterate over the bins like so

ibins = numpy.arange(start = 19, stop = 67, step = 2)
a = 50
for idx, val in enumerate(ibins) :
    if idx > 0:
        if ibins[idx - 1] <= a < ibins[idx] : 
            #do something more meaningfull
            print('Hello')

However, reading on various posts it is my understanding that using the index to access the bin elements is considered 'bad form' in Python.

What I would like to do is something more like this

for ibin in ibins
    if a is in ibin #somehow determine if a is in the bin
        print('Hello')

Is there a reasonable, short way to achieve this? Or is my first suggestion the best way to go.

I do not want to create custom interval-objects or things of that sort.

`bin` is a keyword in python! try to avoid keywords as variable names. — hiro protagonist, Dec 29 '16 at 10:19
@hiroprotagonist Thanks. I have edited my post according to your comment. — mortysporty, Dec 29 '16 at 10:56

Anish Shah · Accepted Answer · 2016-12-29T10:14:48.697

1

start = 19
stop = 67
step = 2

for bin in [range(i, i+step) for i in range(start, stop, step)]:
    if a in bin:
        print('Hello')

If you're using Python 2, then xrange method is better than range.

edited Dec 29 '16 at 10:14

answered Dec 29 '16 at 10:07

Anish Shah

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you meant `if a in bin`? (SO doesnt allow edits of less than 6 chars hence commenting instead of directly editing) – Anupam Dec 29 '16 at 10:12
1

Yes... this is what I want :) Thanks! – mortysporty Dec 29 '16 at 10:52

score 1 · Answer 2 · answered Dec 29 '16 at 10:40

there is a discussion of this here: Iteration over list slices

this is one of the shortest versions:

import numpy as np

lst = np.arange(start = 19, stop = 67, step = 2)
bin_width = 5
search = 50

for ibin in zip(*(iter(lst),) * bin_width):
    print(ibin)
    if min(ibin) <= search <= max(ibin):
        print('found!')
    # or this? not sure what you want...
    if ibin[0] <= search <= ibin[-1]:
        print('found!')

this prints

(19, 21, 23, 25, 27)
(29, 31, 33, 35, 37)
(39, 41, 43, 45, 47)
(49, 51, 53, 55, 57)
found!
found!

How to properly iterate over intervals in Python?

2 Answers2