def concat_files():
    filenames = ['file1.txt', 'file2.txt']
    with open('path/to/output/file', 'w') as outfile:
        for fname in filenames:
            with open(fname) as infile:
                for line in infile:
                    outfile.write(line)

def concat_binary_files():
    with open('output_file.txt','wb') as wfd:
    for f in ['seg1.txt','seg2.txt','seg3.txt']:
        with open(f,'rb') as fd:
            shutil.copyfileobj(fd, wfd)