如何编辑此替换代码以仅替换 n 行

Question

the code I am working with essentially is supposed to go into a file ('Coincount.txt') and for nth line, if in its 4th portion (hence the 3) the string is equal to the variable named 'target', replace the fourth portion with the replacement.

import fileinput
if number_of_bags.is_integer():
    target, replacement = 'N', 'Y'
else:
    target, replacement = 'Y', 'N'

with fileinput.FileInput('CoinCount.txt', inplace=True) as fileobj:
    for n,line in enumerate(fileobj):
        words = line.rstrip().split(',')
        if words[3] == target:
            words[3] = replacement
        print(','.join(words))

    f = fileobj.lineno()  # Number of lines processed.
i = i + 1

print(f'Done, {f} lines processed')

also please know that the txt file is designed like such:

Abena,5p,325.00,Y
Malcolm,1p,3356.00,Y
Jane,£2,120.00,Y
Andy,£1,166.25,N
Sandip,50p,160.00,Y
Liz,20p,250.00,Y
Andy,20p,250.00,Y
Andy,50p,160.00,Y
Jane,£1,183.75,N

the 4th portion represents the 'Y' or 'N'

this is also apart of a bigger function but all that you need to know is that number_of_bags is a variable to the line that is being scanned which is how this thing works.

Please tell me how I need to restructure this code or implement a new line within it so that it works properly.

at the moment if I input this, the output in the txt file is:

Abena,5p,325.00,Y
Malcolm,1p,3356.00,Y
Jane,£2,120.00,Y
Andy,£1,166.25,Y
Sandip,50p,160.00,Y
Liz,20p,250.00,Y
Andy,20p,250.00,Y

this happens due to the .join as it replaces all of the 4th portions of the lines to replacement . I want to know how I can make this function only target nth line so that every line will either replace the 4th portion or will just leave it if it is already input correctly.

Answer 1

if i get your question right you want to only change one line that, so lets say you have this:

line_to_replace = 3 # var that will incidate what line you want to change

so you can change your code:

for n,line in enumerate(fileobj):

into:

for n,line in enumerate(fileobj):
    if n == line_to_replace: # simple if to check the current line number
        ...code...