Need a specific sort of string modification. Can someone help?

[Frank Millman]

On 05/01/2013 10:35, Sia wrote:
> I have strings such as:
>
> tA.-2AG.-2AG,-2ag
> or
> .+3ACG.+5CAACG.+3ACG.+3ACG
>
> The plus and minus signs are always followed by a number (say, i). I want python to find each single plus or minus, remove the sign, the number after it and remove i characters after that. So the two strings above become:
>
> tA..,
> and
> ...
>
> How can I do that?
> Thanks.
>

Here is a naive solution (I am sure there are more elegant ones) -

def strip(old_string):
     new_string = ''
     max = len(old_string)
     pos = 0
     while pos < max:
         char = old_string[pos]
         if char in ('-', '+'):
             num_pos = pos+1
             num_str = ''
             while old_string[num_pos].isdigit():
                 num_str += old_string[num_pos]
                 num_pos += 1
             pos = num_pos + int(num_str)
         else:
             new_string += old_string[pos]
             pos += 1
     return new_string

It caters for the possibility that the number following the +/- could be 
greater than 9 - I don't know if you need that.

It works with your examples, except that the second one returns '....', 
which I think is correct - there are 4 dots in the original string.

HTH

Frank Millman