逐行搜索正则表达式，并在匹配后打印多行

Question

just started writing scripts.

I am trying to write 4 lines after matching a regex in the first line and do this through a very large file with thousands of lines.

#!/usr/local/bin/python
import sys
import string
import re

print"what file would you like to search?"
filename = sys.stdin.readline()
filename = filename.rstrip()
print "enter a barcode"
barcode=sys.stdin.readline()
barcode=barcode.rstrip()
regex=":0:"+barcode
infile = open(filename, "r")
outfile = open("sample_write.fastq", "w")
regex_object = re.compile(regex, re.I)
for line in infile:
   m=regex_object.search(line)
   if m:
      outfile.write(line)
exit

This writes the lines that have matched string (barcode) into my outfile, however, I need to write both the line with the barcode and the following 3 lines after the match into my target file. Any idea ?

Answer 1

You can use the following to match

.*(BARCODE).*\n.*\n.*\n.*    //replace BARCODE with your variable

and write the matches ( \\0 ) to your target file

See DEMO

Edit: Use regex =".*("+barcode+").*\\n.*\\n.*\\n.*"