Is this what you're looking for?
Unfortunately you didn't specify how you know which regexes are supposed to be applied, so I put them into a list of tuples (first element is the regex, second is the replacement text).
import os, os.path, re
path = "/Users/mypath/testData"
myfiles = os.listdir(path)
# its much faster if you compile your regexes before you
# actually use them in a loop
REGEXES = [(re.compile(r'dog'), 'cat'),
(re.compile(r'123'), '789')]
for f in myfiles:
# split the filename and file extension for use in
# renaming the output file
file_name, file_extension = os.path.splitext(f)
generated_output_file = file_name + "_regex" + file_extension
# As l4mpi said ... if odt is zipped, you'd need to unzip it first
# re.search is slower than a simple if statement
if file_extension in ('.txt', '.doc', '.odt', '.htm', '.html'):
# Declare input and output files, open them,
# and start working on each line.
input_file = os.path.join(path, f)
output_file = os.path.join(path, generated_output_file)
with open(input_file, "r") as fi, open(output_file, "w") as fo:
for line in fi:
for search, replace in REGEXES:
line = search.sub(replace, line)
fo.write(line)
# both the input and output files are closed automatically
# after the with statement closes
