Iteration within re.sub()?

[Bryant Huang]

Hi,

Is it possible to perform iteration within the re.sub() function call?

For example, if I have a string like:

str = "abbababbabbaaa"

and I want to replace all b's with an integer that increments from 0,
could I do that with re.sub()?

Replacing b's with 0's is trivial:

i = 0
pat = re.compile("b")
print pat.sub(`i`, str)

Now, how can I increment i in each replacement? Is this possible? Like,
using a lambda function, for example? Or do I use a different re
function altogether?

I use this trivial [ab]* language for simplicity, but I have a real
problem where I need to match a more complex regex and replace it with
an incrementing integer.

Thanks so much!
Bryant