text: # coding: utf-8
  
  import re
  
  text = 'yeah, but no, but yeah, but no, but yeah'
  print(text.replace('yeah', 'yep'))
  
  text = 'Today is 11/27/2012. PyCon starts 3/13/2013.'
  print(re.sub(r'(\d+)/(\d+)/(\d+)', r'\3-\1-\2', text))  # re 模块中的 sub做匹配
  
  text = 'UPPER PYTHON, lower python, Mixed Python'
  re.findall('python', text, flags=re.IGNORECASE)  # 忽略大小写
  
  s = ' hello   world \n'
  s = s.strip()
  print(s)
  re.sub(r'\s+', '', s)
  print(s)
  
  s = 'hello world'
  s.center(20, '*')
  print(s)