import re

#variables to set
origFileName = "orig.txt"
newFileName = "new.txt"
relfirst = "relfirst"
relsecond = "relsecond"

#Reads the old file in, probably slow if your file is very big, but you didn't specify that
textfile = open(origFileName, 'r')
filetext = textfile.read()
textfile.close()

#This is called a regular expression, its a fancy way to find something, look it up online
pattern = re.compile("(?<=<"+relfirst+">).*?(?=</"+relfirst+">)|(?<=<"+relsecond+">).*?(?=</"+relsecond+">)",re.DOTALL)
matches = pattern.findall(filetext)

if(len(matches)>0):
    #open the new file where we write the result
    newfile = open(newFileName,'w')

    #write the start of the thing, you might want to tweak this
    newfile.write("""<?xml version="1.0"?>
<fixed>
    <useless>0</useless>""")
    i=0
    #Run through all the items in the file
    while i < len(matches):
        firstStringYouWanted = matches[i];
        secondStringYouWanted = matches[i+1];

        #Write each item into new file, you might want to tweak the stuff below
        newfile.write("""
    <fixeditem>
        <type>s</type>
        <first>"""+firstStringYouWanted+"""</first>
        <second>"""+secondStringYouWanted+"""</second>
    </fixeditem>""")
        i=i+2
    #write the last part, you might want to tweak this
    newfile.write("\n</fixed>")
    newfile.close()
    print("Sucessfully searched/replaced everything")
else:
    print("No match found")