【python cookbook】【字符串与文本】5.查找和替换文本

问题：对字符串中的文本做查找和替换

解决方案：

1、对于简单模式：str.replace(old, new[, max])

2、复杂模式：使用re模块中的re.sub(匹配的模式, newstring, oldstring[，替换个数])函数

3、re.subn()可以获得替换的总次数

# example.py
#
# Examples of simple regular expression substitution

import re

#simple sample
text1='yeah,but no,but yeah,but no,but yeah,but no,but yeah'
print (text1.replace('yeah','yeh'))
print (text1.replace('no','yes',2))
print ('---------------------------')
# Some sample text
text = 'Today is 11/27/2012. PyCon starts 3/13/2013.'
datepat = re.compile(r'(\d+)/(\d+)/(\d+)')
# (a) Simple substitution \3-表示匹配的模式中第3个模式组
print(datepat.sub(r'\3-\1-\2', text))  #等价于print (re.sub(r'(\d+)/(\d+)/(\d+)',r'\3-\1-\2', text))
print ('*****************************')
# (b) Replacement function  替换回调函数
from calendar import month_abbr
def change_date(m):
    mon_name = month_abbr[int(m.group(1))]
    return '{} {} {}'.format(m.group(2), mon_name, m.group(3))

print(datepat.sub(change_date, text))
print (re.sub(r'(\d+)/(\d+)/(\d+)',change_date, text))
print ('++++++++++++++++++++++++++++++++')

# 通过re.subn()获取替换的总次数

newtext,n=datepat.subn(r'\3-\1-\2', text) 
print (newtext) 
print (n)

>>> ================================ RESTART ================================
>>>
yeh,but no,but yeh,but no,but yeh,but no,but yeh
yeah,but yes,but yeah,but yes,but yeah,but no,but yeah
---------------------------
Today is 2012-11-27. PyCon starts 2013-3-13.
*****************************
Today is 27 Nov 2012. PyCon starts 13 Mar 2013.
Today is 27 Nov 2012. PyCon starts 13 Mar 2013.
++++++++++++++++++++++++++++++++
Today is 2012-11-27. PyCon starts 2013-3-13.
2
>>>