fname = '123.txt'

# 写入文件内容
data = '\n'.join([f'第{i}行内容' for i in range(10)])
with open(fname, 'w') as f:
    f.write(data)

# 读取文件内容
with open(fname) as f:
    data2 = f.read()
    for line in data2.split('\n'):
        print(line)