Python/Regex

To Match

import re

sample1 = '2018-05-31'
sample2 = 'Today is 2018-51-31.'
pattern = re.compile('\d{4}-\d{2}-\d{2}')

m = pattern.search(sample1)
if m:
    print('Found pattern in sample1.')
    print('m[0]={}, m[1]={}, m[2]={}'.format(m[0], m[1], m[2]))

m = pattern.search(sample2)
if m:
    print('Found pattern in sample2.')
    print('m[0]={}, m[1]={}, m[2]={}'.format(m[0], m[1], m[2]))

m = pattern.match(sample1)
if m:
    print('Match pattern sample1.')
    print('m[0]={}, m[1]={}, m[2]={}'.format(m[0], m[1], m[2]))

m = pattern.match(sample2)
if m:
    print('Match pattern sample2.')
    print('m[0]={}, m[1]={}, m[2]={}'.format(m[0], m[1], m[2]))

To Replace

ns = re.sub('o+', '_', 'doooooog')