Please help me optimize my Python code

Question

Beginner here! Forgive me in advance for raising what is probably an incredibly simple problem.

I've been trying to put together a Python script that runs multiple find-and-replace actions and a few similar things on a specified plain-text file. It works, but from a programming perspective I doubt it works well. How would I best go about optimizing the actions made upon the 'outtext' variable? At the moment it's basically doing a very similar thing four times over...

import binascii
import re
import struct
import sys

infile = sys.argv[1]
charenc = sys.argv[2]
outFile=infile+'.tex'

findreplace = [
('TERM1', 'TERM2'),
('TERM3', 'TERM4'),
('TERM5', 'TERM6'),
]

inF = open(infile,'rb')
s=unicode(inF.read(),charenc)
inF.close()

# THIS IS VERY MESSY.
for couple in findreplace:
    outtext=s.replace(couple[0],couple[1])
    s=outtext

for couple in findreplace:
    outtext=re.compile('Title: (.*)', re.I).sub(r'\\title'+ r'{\1}', s)
    s=outtext

for couple in findreplace:
    outtext=re.compile('Author: (.*)', re.I).sub(r'\\author'+ r'{\1}', s)
    s=outtext

for couple in findreplace:
    outtext=re.compile('Date: (.*)', re.I).sub(r'\\date'+ r'{\1}', s)
    s=outtext
# END MESSY SECTION.

outF = open(outFile,'wb')
outF.write(outtext.encode('utf-8'))
outF.close()

Answer 1

For the last three replacements, the for-loop seems to be unnecessary, since the loop body doesn't use the loop variable. Also it is not necessary to assign the result to a temporary outtext variable, it can be directly assigned to s .

These changes make the code much more concise:

for couple in findreplace:
    s = s.replace(couple[0],couple[1])

s = re.compile('Title: (.*)', re.I).sub(r'\\title {\1}', s)
s = re.compile('Author: (.*)', re.I).sub(r'\\author {\1}', s)
s = re.compile('Date: (.*)', re.I).sub(r'\\date {\1}', s)

Answer 2

Some possibilities:

• Do the re.compile outside the loop.
• Use only one loop and do all four things inside it.
• Use one regex, which matches on either Title, Author or Date.
• Don't do the last three replaces inside a loop, since they do not use the couple variable.

Answer 3

your code is not so bad. If you want to optimise for speed then I would look into compiling your regex's at the start of the program.

Also, If you want to tidy up your code then chain all your subs together in one loop.