用同一行另一位置的字符串替换文件中某一行位置的字符串-python

Question

I'm working with a huge text file, and i'm trying to replace the string that is in position 0 with the string that is in position 3 using python. I know i can use a simple replace function, but that means i would have to find every individual value, since not every line in the file is similar.

file:

1, 2, 3, Denver, Austin, Miami

3, 2, 1, Denver, Austin, Miami

Denver, Austin, Miami, 1, 2, 3

Need new file to be:

Denver, 2, 3, Denver, Austin, Miami

Denver, 2, 1, Denver, Austin, Miami

1, Austin, Miami, 1, 2, 3

Answer 1

If every line is consistently in that format, you should be able to do something like this:

with open('myfile.txt') as infile, open('myfile_new.txt', 'w') as outfile:
    for line in infile:
        parts = line.split(', ')
        parts[0] = parts[3]
        replacement_line = ', '.join(parts)
        outfile.write(replacement_line)

At the end, you can rename myfile_new.txt to myfile.txt if you like.