【求助】python如何实现字符串和数字的转换

从文件读取出字符串 要把一部分实现++，
举例：AT005CC56，要把AT后面的数字++，改成006，再写回去

要把字符串转换成数字，再转回去，求教大侠如何实现，多谢

---

这样是否满足？！
Python code:

>>> STR
'AT005CC56'
>>> m = re.findall('[0-9]+',STR)
>>> m[0]=(int(m[0])+1).__str__().rjust(3, '0')
>>> s = re.sub(re.findall('[0-9]+',STR)[0], m[0], STR)
'AT006CC56'

---

用正则吧：
Python code:
import re
a = 'AT005CC56'
reg = re.compile(r'AT(\d+?)[^\d]+?\d*')
match = reg.search(a)
if match is not None:
num = match.groups()[0]
format = 'AT%' + '0%dd' % len(num)
a = reg.sub(format % (int(num)+1), a)

print a

---

我的有一点点问题，修正一下：
Python code:
import re
a = 'AT005CC56'
reg = re.compile(r'AT(\d+?)[^\d]+?.*')
match = reg.search(a)
if match is not None:
num = match.groups()[0]
format = '%' + '0%dd' % len(num)
a= a.replace(num, format % (int(num)+1))

print a

---

import re
stram='abc12def000007bcdAB005ABC62b'
fi=re.findall(r'[0-9]+',stram)
for e