does \1 in re work?

[Michael P. Soulier]

    Hello. 

    Looking at the documentation for python 1.5.2, the now aging version that
I'm using, in the re module it states that the standard \1, \2 keys that
reference that matched value in parenthesis in the pattern do in fact work, as
do \g<1>, \g<2>, etc. 

    So, I tried this:

    new = re.sub("^(-?\d+)(\d{3})", '\1,\2', amount)

    new always ended up being '\001,\002'. Not what I wanted.

    So, I used the alternate...

    new = re.sub("^(-?\d+)(\d{3})", '\g<1>,\g<2>', amount)

    Which worked perfectly, giving me, for example, 

    '100000,000' where amount was '100000000'. 

    So, my question is, what was wrong with my first pattern? 

    Thanks very much,

    Mike

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