Python file copying using regex -

i have large log file. want extract lines containing java/javax/or/com followed ./:. every line this, want extract of corresponding lines stack traces , starts at. example:

line1: java.line.something.somethingexception line 2: @ something line 3: @ something line 4: @ something  line 5-20:junk don't want extract. line 21: javax.line.something.somethingexception line 22: @ something line 23: @ something line 24: @ something 

and on...

here want copy line 1-4 , again line 21-24. far code collects line contains keywords i'm unable figure out how write specific no of lines after that, skip few lines , start writing again.these lines starts @ random, i.e can 100 lines or can 250 lines, no pattern.

here's code:

import re import sys itertools import islice  file = open(sys.argv[1], "r") file1 = open(sys.argv[2],"w") = 0 line in file:     if re.search(r'[java|javax|org|com]+?[\.|:]+?', line, re.i) , not (re.search(r'at\s', line, re.i) or re.search(r'mdcloginid:|webcontainer|c\.h\.i\.h\.p\.u\.e|threadpooltaskexecutor|caused\sby', line, re.i)):           file1.write(line) 

this code extracts lines containing keywords, i'm stuck @ how next part,i.e copy next lines containing @ , write them new file, stop 'at' ends. search next line containing keywords , same action again.

this can solved flag set in case match specific conditions:

java_regex = re.compile(...)  # java  at_regex = re.compile(...)    # @  copy = false  # flag control copy or not copy output  line in file_in:    if re.search(java_regex, line):        # start copying if "java" in input        copy = true    else:        if copy , not re.search(at_regex, line):            # stop copying if "at" not in input            copy = false     if copy:        file_out.write(line)