How to replace() a specific value within a list item directly after a keyword

Question

Currently have a standard txt-style file that I'm trying to open, copy, and change a specific value within. However, a standard replace() fn isn't producing any difference. Here's what the 14th line of the file looks like:

 '    Bursts: 1 BF: 50 OF: 1  On: 2 Off: 8'

Here's the current code I have:

conf_file = 'configs/m-b1-of1.conf'
read_conf = open(conf_file, 'r')
conf_txt = read_conf.readlines()

conf_txt[14].replace(conf_txt[14][13], '6')

v_conf

Afterwards, though, no changes have been applied to the specific value I'm referencing (in this case, the first '1' in the 14th line above.

Any help would be appreciated - thanks!

Answer 1

There are few things here I think:

1. I copied your string and the first 1 is actually character 12
2. replace result needs to be assigned back to something (it gives you a new string)
3. replace, will replace all "1"s with "6"s!

Example:

>>> a = '    Bursts: 1 BF: 50 OF: 1  On: 2 Off: 8'
>>> a = a.replace(a[12], '6')
>>> a
'    Bursts: 6 BF: 50 OF: 6  On: 2 Off: 8'

If you only want to replace the first instance (or N instances) of that character you need to let replace() know:

>>> a = '    Bursts: 1 BF: 50 OF: 1  On: 2 Off: 8'
>>> a = a.replace(a[12], '6', 1)
>>> a
'    Bursts: 6 BF: 50 OF: 1  On: 2 Off: 8'

Note that above only "Bursts" are replaced and not "OF"

Answer 2

try this

conf_file = 'configs/m-b1-of1.conf'
read_conf = open(conf_file, 'r')
conf_txt = read_conf.readlines()

conf_txt[14] = conf_txt[14].replace(conf_txt[14][13], '6')

the replace function does not edit the actual string, it just returns the replaced value, so you have to redefine the string in the array