How to convert string with numeric range into a list in Python

Question

I want to have yourfeedback. I need to process an input which is a range defined as string:

targets = 'machine[7:10]'

The result that I need is:

results = ['machine07', 'machine08', 'machine09', 'machine10']

Here is what I have coded in Python:

for target in targets:

    m = re.search('\\d+:\d+\]', target)
    if m:
        name = target.split('[')[0]
        target_range = re.findall('[0-9]+', target)
        print(target_range)
        target_range = [int(i) for i in target_range]
        for tgt in range(target_range[0],target_range[1]+1):
             results.append(name + str(format(tgt, '02d')))

Please, can you tell me is there is a more elegant way or pythonic way of doing the same thing ? ... with NO import module! Thank you.

I'm guessing they mean "nothing which needs an extra library to be installed" — SiHa
– SiHa, Commented Feb 10, 2017 at 13:04

Mohammad Yusuf · Accepted Answer · 2017-02-10 13:06:52Z

3

Capture the desired substrings in 3 groups. Generate a range object by the last 2 groups by converting them to int.

Then run a for loop on the range object and append to the first group.

You can try something like this:

import re

targets = 'machine[7:10]'
a,b,c = re.findall(r'(.*?)\[(\d+):(\d+)\]', targets)[0]
res = [a+'{:0>2}'.format(d) for d in range(int(b),int(c)+1)]
print res

Output:

['machine07', 'machine08', 'machine09', 'machine10']

edited Feb 10, 2017 at 13:06

answered Feb 10, 2017 at 13:00

Mohammad Yusuf

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Mohammad Yusuf · Accepted Answer · 2017-02-10 13:04:03Z

1

You can use groups:

> targets = 'machine[7:10]'
> m = re.match(r'(\w+)\[(\d+):(\d+)\]', targets)
> results = ['{}{:0>2}'.format(m.group(1), str(i)) for i in range(int(m.group(2)), int(m.group(3))+1)]
> results
['machine07', 'machine08', 'machine09', 'machine10']

edited Feb 10, 2017 at 13:04

Mohammad Yusuf

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answered Feb 10, 2017 at 12:59

user2390182

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Comments

glibdud · Accepted Answer · 2017-02-10 13:06:51Z

0

You already used split() in your code, why not just take that a step farther and eliminate the need for re?

(base, indices) = targets.split('[')
(start, end) = indices[:-1].split(':')

target_range = []
for i in range(int(start), int(end)+1):
    target_range.append('{0}{1:02}'.format(base, i))

answered Feb 10, 2017 at 13:06

glibdud

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Comments

Rahul K P · Accepted Answer · 2017-02-10 13:07:54Z

0

Try this,

word,nums_ = targets.split('[')
nums = map(int,nums_.replace(']','').split(':'))
nums[-1] = nums[-1]+1
print [word+'{:0>2}'.format(i) for i in range(*nums)]

result

['machine07', 'machine08', 'machine09', 'machine10']

answered Feb 10, 2017 at 13:07

Rahul K P

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ooknosi · Accepted Answer · 2017-02-10 13:12:25Z

0

List comprehension combined with some string splicing is one way to do it without importing anything:

targets = 'machine[7:10]'

start_idx = targets.index('[')
separator_idx = targets.index(':')
end_idx = targets.index(']')

name = targets[:start_idx]
range_start = int(targets[start_idx + 1:separator_idx])
range_end = int(targets[separator_idx + 1:end_idx]) + 1

results = [name + "{:02}".format(i) for i in range(range_start, range_end)]

print(results)

edited Feb 10, 2017 at 13:12

answered Feb 10, 2017 at 12:54

ooknosi

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3 Comments

ooknosi Over a year ago

Hang on a moment I accidentally hit submit. I'm in the midst of editing my answer.

Ep1c F4iL Over a year ago

OK fine but you are using hardcoded value ... such as machine and 7,11 ! I should have specified that from the string itself you need to extract the information. What if my string is : server[1:25] !

ooknosi Over a year ago

@Ep1cF4iL Refresh to see my solution please.

PdevG · Accepted Answer · 2017-02-10 13:19:36Z

0

First split into range and target:

target, ranges = targets[:-1].split('[')

Then get low and high range:

range_min, range_max = [int(i) for i in ranges.split(':')]

Then loop over range and create string:

results = ['{}_{:0>2}'.format(target, i) for i in range(range_min, range_max + 1)]

results:

['machine_07', 'machine_08', 'machine_09', 'machine_10']

edited Feb 10, 2017 at 13:19

answered Feb 10, 2017 at 13:14

PdevG

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Comments

alec_djinn · Accepted Answer · 2017-02-10 13:26:14Z

0

I prefer something more readable, try to use the new way of formatting strings, it makes everything much clear.

targets = 'machine[7:10]'
results = []

name, range_ = targets.split('[')
idx = [int(x) for x in range_[:-1].split(':')]

for i in range(idx[0],idx[1]+1):
    if i < 10:
        results.append(f'{name}0{i}')
    else:
        results.append(f'{name}{i}')

>>>results
>>>['machine07', 'machine08', 'machine09', 'machine10']

answered Feb 10, 2017 at 13:26

alec_djinn

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