Situation:

* text: a string
* R: a regex that matches part of the string. This might be expensive to calculate.

I want to both delete the R-matches from the text, and see what they actually contain. Currently, I do this like:

```
import re
ab_re = re.compile("[ab]")
text="abcdedfe falijbijie bbbb laifsjelifjl"
ab_re.findall(text)
# ['a', 'b', 'a', 'b', 'b', 'b', 'b', 'b', 'a']
ab_re.sub('',text)
# 'cdedfe flijijie  lifsjelifjl'

```

This runs the regex twice, near as I can tell. Is there a technique to do it all on pass, perhaps using re.split? It seems like with split based solutions I'd need to do the regex at least twice as well.