Getting minutes from string via regex

Question

I have task to be done. I have test file for it which is containing code:

import unittest
from Task302 import extract_minutes

class Task302Test(unittest.TestCase):
    """Testy do zadania 302"""

    def test_simple(self):
        """Prosty test."""
        self.assertEqual(extract_minutes("9:13"), "13")
        self.assertEqual(extract_minutes("18:44"), "44")
        self.assertEqual(extract_minutes("23:59"), "59")
        self.assertEqual(extract_minutes("0:00"), "00")
        self.assertEqual(extract_minutes("25:14"), "<NONE>")
        self.assertEqual(extract_minutes("9:61"), "<NONE>")
        self.assertEqual(extract_minutes("x9:13y"), "<NONE>")

I have written code:

def extract_minutes(string):
    pattern = '[0-1]*[0-9]+|2[0-3]:([0-5][0-9])'
    r = re.compile(pattern)
    m = r.search(string)
    if m:
        return m.group(1)
    else:
        return "<NONE>"

Please explain me what is wrong with my code and how to fix it.

Please explain to us as to what errors are there so that we can explain to you what is wrong with your code — Bhargav Rao
– Bhargav Rao, Commented Dec 25, 2014 at 18:45
@Cris because this 2[0-3]:([0-5][0-9]) part of your regex won't match the starting 9 . That's what i explained. — Avinash Raj
– Avinash Raj, Commented Dec 25, 2014 at 19:02
how to make or operator (|) local? ([0-1]*[0-9])+|(2[0-3]), but without parentheses that will make values avaible by group method? — krzyhub
– krzyhub, Commented Dec 25, 2014 at 19:06

Avinash Raj · Accepted Answer · 2014-12-25 19:04:52Z

2

You need to put the | operator only for the hours. Your regex [0-1]*[0-9]+|2[0-3]:([0-5][0-9]) considers the hours from 0 to 19 as separate part and hours from 20 to 23 plus the minutes as separate part. And also i suggest you to put ? instead of * because * will match the previous token zero or more times, where the ? (except as a non-greedy quantifier) will match the previous token 0 or 1 times. And you must need to remove the + after the character class [0-9] because + matches the previous token one or more times.

pattern = r'\b(?:[0-1]?[0-9]|2[0-3]):([0-5][0-9])\b'

\b called word boundary which matches between a word character and a non-word character. Without word boundaries, it would match this x9:13y string.

DEMO

edited Dec 25, 2014 at 19:04

answered Dec 25, 2014 at 18:47

Avinash Raj

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1 Comment

krzyhub Over a year ago

yeah, you got it, i will check it more in details, because i hae more tasks. thank you

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