使用Python将文本中的行与未知行交换

Question

I have 5 big text files, and I want to copy only one line from one of the files, and replace the same lines in the other files. Each line starts the same, only the end is different, and the line is unique.

After browsing many options, this is what I got now (for one of the files):

with open(fileNumberOne) as f1:
    for line1 in f1:
        if "FUSE_ROOT_DIR = " in line1:
            with open(fileNumberTwo) as f2:
                for line2 in f2:
                    newText = f2.read()
                    if "FUSE_ROOT_DIR = " in line2in :
                        newText = f2.read().replace(line2in , line1)
                    with open(fileNumberTwo, "w") as f2:
                        f2.write(newText)

"FUSE_ROOT_DIR = " is the identifier for the line that needs to be changed, the value from fileNumberOne is the correct one, and I need to swap the value for fileNumberTwo, and the line is unique so no need to worry about getting suddenly 2 lines that include the words "FUSE_ROOT_DIR".

The result is that the line won't change, and also the first line in fileNumberTwo is deleted (it starts with ###, maybe it has something to do with it?).

Any ideas?

Thanks!

Answer 1

an illustration of my comment: you could do it in two steps, eg

token = 'FUSE_ROOT_DIR '
with open(file1, 'r') as fobj: # 1 - find your "reference" line
    for line in fobj:
        if token in line:
            ref_line = line
            break # skip the rest of the lines

if ref_line: # 2 - if it was found, replace it in the other files  
    with open(file2, 'r+') as fobj: # loop this for all your other files
        content = fobj.readlines() # read everything to a variable and modify that
        content = [ref_line if token in l else l for l in content]
        fobj.seek(0) # reset file pointer to beginning of file
        fobj.writelines(content) # overwrite with modified content

Another option for step #2 would be to use the fileinput module to do the replacement "in-place":

import fileinput        

with fileinput.input(file2, inplace=True) as f:
    for line in f:   
        if token in line:
            line = ref_line
        print(line.strip())