Python 3.7 - 在文件夹中 all.txt 文件的每一行开头插入文件名

Question

Python 3.7 - insert filename at the start of every line to all.txt files in a folder.

I have a few differently named.txt files in a folder. I would like to insert the filename to the beginning of each line in each.txt file.

So far all I've been able to do is insert numbers which I found from another post. The below code works well for this, however I've been unable to find a way to insert the open filename:

import os

def add_numbers(filename):
    with open(filename, 'r') as readfile:
        data = readfile.readlines()
    with open(filename, 'w') as writefile:
        for i, line in enumerate(data):
            writefile.write('%d. %s' % (i + 1, line))

for path, _, filenames in os.walk('.'):
    for filename in filenames:
        add_numbers(os.path.join(path, filename))

Answer 1

import os

def add_numbers(filename):
    with open(filename, 'r') as readfile:
        data = readfile.readlines()
    with open(filename, 'w') as writefile:
        for i, line in enumerate(data):
            writefile.write('%s. %s' % (filename, line))

for path, _, filenames in os.walk('.'):
    for filename in filenames:
        add_numbers(os.path.join(path, filename))