Replace based on values in a file

[WJSwan]

Here is what I tried, but it does not seem to work.

# Convert
import codecs
import re
def FixXrefs(xref):
      global bookname
      global bookno
      lg.write("----- Entered function\n")
      instuff=xref
      otstuff=""
      n=len(bookname)
      for i in bookno:
          j=int(i)-1
          pattern = bookname[j]+" "
          replaceWith = i+"."
          lg.write("|"+pattern+"|"+replaceWith+"|\n")
          otstuff=instuff.replace(pattern, replaceWith)
      instuff=otstuff.replace(":", ".")
      return instuff
             
lg=open("log.txt", "w")
bookname=[]
bookno=[]
#set up bookname/bookno table
bn=codecs.open("Boeke.txt", "r", "utf-8")
while True:
      l=bn.readline()
      l.strip('\n')
      if ("" == l):
            lg.write("End of bookname/no file reached\n")
            break
      #parse string
      words = l.split(",")
      bookno.append(words[0])
      bookname.append(words[2])
bn.close()
# Now read the file to reformat
fn=codecs.open("Conv.txt", "r", "utf-8")
while True:
      irec=fn.readline()
      pline="INREC\n"+irec
      lg.write(pline)
      if ("" == irec):
        lg.write ("End of Conv file reached\n")
        break;
      nxref = FixXrefs(irec)
      pline="NXREF\n"+nxref
      lg.write(pline)
lg.close()
fn.close()