Read in file - change contents - write out to same file

Question

I have to read in a file, change a sections of the text here and there, and then write out to the same file.

Currently I do:

f = open(file)
file_str          


        

Answer 1

That looks straightforward, and clear already. Any suggestion depends on how big the files are. If not really huge that looks fine. If really large, you could process in chunks.

But you could use a context manager, to avoid the explicit closes.

with open(filename) as f:
    file_str = f.read()

# do stuff with file_str

with open(filename, "w") as f:
    f.write(file_str)

Answer 2

If you work line by line you can use fileinput with inplace mode

import fileinput

for line in fileinput.input(mifile, inplace=1):
    print process(line)

if you need to process all the text at once, then your code can be optimized a bit using with that takes care of closing the file:

with open(myfile) as f:
    file_str = f.read()
#
do_actions_on_file_str
#
with open(myfile, 'w') as f:
    f.write(file_str)