python search in file and edit code example

Example 1: python replace part in large file

for file in files:
    fname = os.path.join(dir, file)
    inFile = codecs.open(fname, "r", "utf-8")
    outFile = codecs.open(fname + ".new", "w", "utf-8")
    for line in inFile:
        newline = do_replacements_on(line)
        outFile.write(newline)
    inFile.close()
    outFile.close()
    os.rename(fname + ".new", fname)

Example 2: python replace text in file

filename = "sample1.txt"
# SAMPLE1.TXT
# Hello World!
# I am a human.

with open(filename, 'r+') as f:
    text = f.read()
    text = re.sub('human', 'cat', text)
    f.seek(0)
    f.write(text)
    f.truncate()

# SAMPLE1.TXT
# Hello World!
# I am a cat.