Flaskでpartial contentを実現

index.py

import mimetypes
import os
import re

from flask import Flask, request, send_file, Response

app = Flask(__name__, static_folder=".", static_url_path='')

@app.after_request
def after_request(response):
    response.headers.add('Accept-Ranges', 'bytes')
    return response

@app.route('/episode.mp3')
def send_file_partial():
    path = './episode.mp3'
    range_header = request.headers.get('Range', None)
    if not range_header:
        return send_file(path)
    
    size = os.path.getsize(path)    
    byte1, byte2 = 0, None
    
    m = re.search('(\d+)-(\d*)', range_header)
    g = m.groups()
    
    if g[0]:
        byte1 = int(g[0])
    if g[1]:
        byte2 = int(g[1])

    length = size - byte1
    if byte2 != None:
        length = byte2 - byte1
    
    data = None
    with open(path, 'rb') as f:
        f.seek(byte1)
        data = f.read(length)

    res = Response(data, 
        206,
        mimetype=mimetypes.guess_type(path)[0], 
        direct_passthrough=True)
    res.headers.add('Content-Range', 'bytes {0}-{1}/{2}'.format(byte1, byte1 + length - 1, size))

    return res
    
app.run(port=8080, debug=True)