import re
 
pattern = r"\(pp\.\s+\d+(?:-\d+)?\)|\b\d+(?:-\d+)?(?=(?:\s*,\s*\d+(?:-\d+)?)*\.)"
 
s = ("- Mitchell, J.A. (2017). Citation: Why is it so important. Mendeley Journal, 67(2), (pp. 81-95). \n\n"
            "- Denhart, H. (2008). Deconstructing barriers: Perceptions of students labeled with learning disabilities in higher education. Journal of Learning Disabilities, 40,41, 483-497.\n\n"
            "(pp. 81). \n"
            "12-12\n"
            "http://t...content-available-to-author-only...t.com/12-23\n\n"
            "Usually the page numbers follow a commas and then there is a dot (like this: , 1-2. ) How can I change the code according to this? Same goes for when there is only one page listed , number. and the ` (pp. 12)` format.")
 
print(re.findall(pattern, s))

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