Have: 

```
f = open(...)  
r = re.compile(...)

```

Need:  

Find the position (start and end) of a first matching regexp in a big file?  

(starting from `current_pos=...`) 

How can I do this? 

---

I want to have this function: 

```
def find_first_regex_in_file(f, regexp, start_pos=0):  
   f.seek(start_pos)  

   .... (searching f for regexp starting from start_pos) HOW?  

   return [match_start, match_end]  

```

File 'f' is expected to be big.