HTTP 206 (Partial Content) For Flask

send_file_partial.py

import mimetypes
import os
import re

from flask import request, send_file, Response

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


def send_file_partial(path, filename, **kwargs):
    range_header = request.headers.get('Range', None)
    if not range_header:
        return send_from_directory(path, filename, **kwargs)

    full_filename = path + '/' + filename

    size = os.path.getsize(full_filename)
    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 is not None:
        length = byte2 - byte1

    data = None
    with open(full_filename, 'rb') as f:
        f.seek(byte1)
        data = f.read(length)

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

    return rv

line 33 should be: length = byte2 + 1 - byte1 instead of length = byte2 - byte1.