Search and match the specified text pattern in the string

For simple literal patterns , Use it directly  str.replace()  The method can , such as ：

>>> text = 'yeah, but no, but yeah, but no, but yeah'
>>> text.replace('yeah', 'yep')
'yep, but no, but yep, but no, but yep'

For complex patterns , Please use  re  Module  sub()  function . To illustrate this , Suppose you want to take the form  11/27/2012  The date string of is changed to  2012-11-27 . Examples are as follows ：

>>> text = 'Today is 11/27/2012. PyCon starts 3/13/2013.'
>>> import re
>>> re.sub(r'(\d+)/(\d+)/(\d+)', r'\3-\1-\2', text)
'Today is 2012-11-27. PyCon starts 2013-3-13.'

sub()  The first parameter in the function is the matched pattern , The second parameter is replace mode . Backslash numbers like  \3  Point to the capture group number of the previous pattern .

If you plan to do multiple substitutions with the same pattern , Consider compiling it first to improve performance . such as ：

>>> import re
>>> datepat = re.compile(r'(\d+)/(\d+)/(\d+)')
>>> datepat.sub(r'\3-\1-\2', text)
'Today is 2012-11-27. PyCon starts 2013-3-13.'