<ref>*Any_Character_Could_Be_Here</ref>

>>> import re
>>> test_string = '''<ref>*Any_Character_Could_Be_Here</ref>
<ref>other characters could be here</ref>'''
>>> re.findall(r'<ref>.*?</ref>', test_string)
['<ref>*Any_Character_Could_Be_Here</ref>', '<ref>other characters could be here</ref>']  # a list of matching strings

if re.search(r"<ref>*[^<]*</ref>", subject):
    # Successful match
else:
    # Match attempt failed