s = "$$$aa1bb2 cc-dd ee_ff ggg."
re.sub(r'\W+', ' ', s).upper()
# ' AA1BB2 CC DD EE_FF GGG '
Is _ punctuation?
re.sub(r'[_\W]+', ' ', s).upper()
# ' AA1BB2 CC DD EE FF GGG '
Don't want the leading and trailing space?
re.sub(r'[_\W]+', ' ', s).strip().upper()
# 'AA1BB2 CC DD EE FF GGG'