import re
txt = (
    """this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>.  and there are many other lines in the txt files with<[3> such tags </[3>"""
    )
out = re.sub('(<[^>]+>)', '', txt)
print(out)
Как ввести регулярное выражение в string.replace?