LookForward

Looking Forward in Text Processing

with Python

A few weeks ago, I designed a tool that used sar and Sun explorer data for analysis. While searching through the data, I needed to grab text between two lines. This presented a problem as I had done this in Perl, but never in Python. The algorithm is basically the same, but Python has better list functionality (in my opinion) which makes the code easier to implement. Below is the module I wrote for this purpose.

import re

import os

import sys

#

def lookForward(searchPattern, endPattern, fileFD):

   '''lookForward takes 3 args: the beginning search pattern,

    second arg is the pattern to stop the search

   third arg is the file object. File must be opened prior to using the module.

   Returns a double list of search elements'''

   firstList = []

   returnValue = []

   for line in fileFD:

      #Replace spaces with commas.

      string = re.sub('\s+', ',', line)

      beginPattern = re.compile(searchPattern)

      beginMatch = re.search(beginPattern, string)

      finalPattern = re.compile(endPattern)

      #if there is a match for the beginning search pattern, then start parsing until endPattern is found.

      if beginMatch:

         #append the beginning search pattern line

         firstList.append(beginMatch.group(0))

         try:

            #endless loop until endPattern is found

            while True:

               #take next line in file

               newLine = fileFD.next()

               #replace spaces with commas

               noSpacesLine = re.sub('\s+', ',', newLine)

               #append each line to first list

               firstList.append(noSpacesLine)

               finalMatch = re.search(finalPattern, noSpacesLine)

               #check if newLine is a match for endPattern

               if finalMatch:

                  #append first list to the returnValue list

                  returnValue.append(firstList)

                  #null firstList so the data is not duplicated on next loop

                  firstList = []

                  #break the inner loop since endPattern was found

                  break

         except StopIteration:

            continue

return(returnValue)