Extracting info from large structured text files

Question

I need to read some large files (from 50k to 100k lines), structured in groups separated by empty lines. Each group start at the same pattern \"No.999999999 dd/mm/yyyy ZZZ

Answer 1

I wouldn't use regex here. If you know that your lines will be starting with fixed strings, why not check those strings and write a logic around it?

for line in open(file):
    if line[0:3]=='No.':
        currIndex='No'
        map['No']=line[4:]
   ....
   ...
   else if line.strip()=='':
       //store the record in the map and clear the map
   else:
      //append line to the last index in map.. this is when the record overflows to the next line.
      Map[currIndex]=Map[currIndex]+"\n"+line 

Consider the above code as just the pseudocode.