error in module re?

[Ken Koller]

I think you need to use a raw string such as r'\2-\1' or escape the slash
'\\2-\\1'

 re.sub('(a+)\s(b+)', r'\2-\1', 'aaa bbb')

or

 re.sub('(a+)\s(b+)', '\\2-\\1', 'aaa bbb')

"Chris..." wrote:

> Dear Pythoners...
>
>   Is this an implementation or documentation error?
> >>> import re
> >>> re.sub('(a+)\s(b+)', '\2-\1', 'aaa bbb')
> '\002-\001'
> instead of
> 'bbb-aaa'
> The documentation says, that you can use backreferences in replacement
> string, but only \g<number> works.
>
>   My version is:
> Python 1.5.2 (#0, Apr 13 1999, 10:51:12) [MSC 32 bit (Intel)] on win32
>
> bye
>   Chris...