CODEWITHSUNDEEP
pythonregex
kbang
kbang

Reputation: 704

regex to match or ignore a set of two digit numbers

I am looking for a regex in python to match everything before 19 and after 24.

File names are test_case_*.py, where the asterisk is a 1 or 2 digit number. eg: test_case_1.py, test_case_27.py.

Initially, I thought something like [1-19] should work,it turned out to be much harder than I thought.

Has any one worked on a solution for such cases?

PS:i am ok even if we can find a one regex for all numbers before a number x and one for all numbers after a number y.

Upvotes: 1

Views: 2084

Answers (3)

Andrew Clark
Andrew Clark

Reputation: 208425

The following should do it (for matching the entire filename):

^test_case_([3-9]?\d|1[0-8]|2[5-9])\.py$

Explanation:

^             # beginning of string anchor
test_case_    # match literal characters 'test_case_' (file prefix)
(             # begin group
  [3-9]?\d      # match 0-9 or 30-99
    |             # OR
  1[0-8]        # match 10-18
    |             # OR
  2[5-9]        # match 25-29
)             # end group
\.py          # match literal characters '.py' (file suffix)
$             # end of string anchor

Upvotes: 2

arshajii
arshajii

Reputation: 129497

I wouldn't use a regex for validating the number itself, I would use one only for extracting the number, e.g.:

>>> import re
>>> name = 'test_case_42.py'
>>> num = int(re.match('test_case_(\d+).py', name).group(1))
>>> num
42

and then use something like:

num < 19 or num > 24

to ensure num is valid. The reason for this is that it's much harder to adapt a regex that does this than it is to adapt something like num < 19 or num > 24.

Upvotes: 3

xanatos
xanatos

Reputation: 111840

Something like

"(?<=_)(?!(19|20|21|22|23|24)\.)[0-9]+(?=\.)"

One or more digits `[0-9]+`
that aren't 19-24 `(?!19|20|21|22|23|24)` followed by a . 
following a _ `(?<=_)` and preceding a . `(?=\.)`

http://regexr.com?35rbm

Or more compactly

"(?<=_)(?!(19|2[0-4])\.)[0-9]+(?=\.)"

where the 20-24 range has been compacted.

Upvotes: 0

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