We have an example .cfg file consisting of key-value pairs. Based on user input, we need to update the value. I’m thinking of updating values using configParser, but the file doesn’t have any parts (e.g. [My Section]). According to the documentation, it needs to set three values – part, key, and value. Unfortunately, I can’t add any section tags because the file is already in use by other tasks.

What is another way we can set values based on keys?

File example

some.status_file_mode    =  1    # Some comment
some.example_time    = 7200     # Some comment 

As required, the line did not change. Spaces and comments need to be left as is.

使用>NamedTemporaryFile It’s not hard to build a simple parser from the tempfile module to update a file that looks like this:

Code:

def replace_key(filename, key, value):
    with open(filename, 'rU') as f_in, tempfile. NamedTemporaryFile(
            'w', dir=os.path.dirname(filename), delete=False) as f_out:
        for line in f_in.readlines():
            if line.startswith(key):
                line = '='.join((line.split('=')[0], ' {}'.format(value)))
            f_out.write(line)

# remove old version
    os.unlink(filename)

# rename new version
    os.rename(f_out.name, filename)

Test code:

import os
import tempfile
replace_key('file1', 'some.example_time', 3)

Result:

some.status_file_mode    = 1
some.example_time    = 3