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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def replace_in_files(search, replace, depth=0, paths=None, confirm=True):
 """ Does a line-by-line search and replace, but only up to the "depth" line. """


    # have the user select some files
    if paths==None:
        paths = _s.dialogs.MultipleFiles('DIS AND DAT|*.*')
    if paths == []: return

    for path in paths:
        lines = read_lines(path)

        if depth: N=min(len(lines),depth)
        else:     N=len(lines)

        for n in range(0,N):
            if lines[n].find(search) >= 0:
                lines[n] = lines[n].replace(search,replace)
                print(path.split(_os.path.pathsep)[-1]+ ': "'+lines[n]+'"')

        # only write if we're not confirming
        if not confirm:
            _os.rename(path, path+".backup")
            write_to_file(path, join(lines, ''))

    if confirm:
        if input("yes? ")=="yes":
            replace_in_files(search,replace,depth,paths,False)

    return