A better RE?

[Fredrik Lundh]

Magnus Lycka wrote:

> I want an re that matches strings like "21MAR06 31APR06 1236",
> where the last part is day numbers (1-7), i.e it can contain
> the numbers 1-7, in order, only one of each, and at least one
> digit. I want it as three groups. I was thinking of
>
> r"(\d\d[A-Z]\d\d) (\d\d[A-Z]\d\d) (1?2?3?4?5?6?7?)"
>
> but that will match even if the third group is empty,
> right? Does anyone have good and not overly complex RE for
> this?

how about (untested)

    r"(\d\d[A-Z]{3}\d\d) (\d\d[A-Z]{3}\d\d)  (?=[1234567])(1?2?3?4?5?6?7?)"

where {3} means require three copies of the previous RE part, and
(?=[1234567]) means require at least one of 1-7, but don't move
forward if it matches.

</F>