python split a string when a keyword comes after a pattern

Question

I have a hostname like

ab-test-db-dev.0002-colo1-vm234.abc.domain.com

(yeah there is no convention followed internally for hostname.)

I was trying to split this hostname to

ab-test-db-dev.0002-colo1-vm234

pattern is to split with the '.', but only if there are no other special characters following that dot.

I tried

pattern = domain.split(".")

but it is taking only till

ab-test-db-dev and not ab-test-db-dev.0002-colo1-vm234

as the first element.

What is the best way to achieve this?

Answer 1

You could remove the first part until no more dashes remain; that'd be the domain name to remove from the hostname:

hostname = domain
while '-' in domain:
    domain = domain.partition('.')[-1]
hostname = hostname[:-len(domain) - 1]

or the other way around, remove the last part if it doesn't contain dashes, with str.rpartition() :

hostname = domain
while True:
    first, _, end = hostname.rpartition('.')
    if '-' in end:
        break
    hostname = first

Using a regular expression looking for any part that only contains letters and dots:

import re

hostname = re.sub(r'\.[a-z.]+$', '', domain)

Demo:

>>> domain = 'ab-test-db-dev.0002-colo1-vm234.abc.domain.com'
>>> hostname = domain
>>> while '-' in domain:
...     domain = domain.partition('.')[-1]
... 
>>> hostname[:-len(domain) - 1]
'ab-test-db-dev.0002-colo1-vm234'
>>> domain = 'ab-test-db-dev.0002-colo1-vm234.abc.domain.com'
>>> hostname = domain
>>> while True:
...     first, _, end = hostname.rpartition('.')
...     if '-' in end:
...         break
...     hostname = first
... 
>>> hostname
'ab-test-db-dev.0002-colo1-vm234'
>>> import re
>>> re.sub(r'\.[a-z.]+$', '', domain)
'ab-test-db-dev.0002-colo1-vm234'

Answer 2

Didn't get the pattern but for this case the following can work.

(?<=\d)\.

Try this:

https://regex101.com/r/rU8yP6/21

Use re.split .

 import re
 re.split(r"(?<=\d)\.",test_Str)

Or

^(.*?)(?!.*-)\.

Try this:

https://regex101.com/r/rU8yP6/22

import re
print re.findall(r"^(.*?)(?!.*-)\.",test_str)

Answer 3

If I understood your question correctly, then this regex should do the job:

.*?(?=\\.(?!.*[^\\w.]))

>>> print re.match(r'.*?(?=\.(?!.*[^\w.]))', 'ab-test-db-dev.0002-colo1-vm234.abc.domain.com')
ab-test-db-dev.0002-colo1-vm234

---

Explanation:

.*? # match everything up to...
(?=
    \. # the first dot...
    (?! # that isn't followed by...
        .* # any text and...
        [^\w.] # something that's not a word character or a dot.
    )
)