replace string in file with using regular expressions [closed]

Answer 1

# The following code will search 'mm/dd/yyyy' (e.g. NOV/30/2016 ),
# and replace with 'mm-dd-yyyy' in multi-line mode.
import re
with open ('input.txt', 'r' ) as f:
    content = f.read()
    content_new = re.sub('(\w{2})/(\d{2})/(\d{4})', r'\1-\2-\3', content, flags = re.M)