问下载的txt文件以html格式查看，但不包括空行

EN

from flask import Flask, send_from_directory

app = Flask(__name__)

@app.route('/file')
def download_file():
    # change app.root_path to whatever the directory actually is
    # this just serves this python file (named example.py) as plain text
    return send_from_directory(
        app.root_path, 'example.py',
        as_attachment=True, mimetype='text/plain'
    )

@app.route('/mem')
def download_mem():
    # instantiate the response class directly
    # pass the mimetype
    r = app.response_class('test data\n\ntest data', mimetype='text/plain')
    # add the attachment header
    r.headers.set('Content-Disposition', 'attachment', filename='test_data.txt')
    return r

app.run('localhost', debug=True)