Given a .torrent file how do I generate a magnet link in python? [closed]

Question

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 8 years ago.

I need a way to convert .torrents into magnet links. Would like a way to do so in python. Are there any libraries that already do this?

Answer 1

You can do this with the bencode module, extracted from BitTorrent.

To show you an example, I downloaded a torrent ISO of Ubuntu from here:

http://releases.ubuntu.com/12.04/ubuntu-12.04.1-desktop-i386.iso.torrent

Then, you can parse it in Python like this:

>>> import bencode
>>> torrent = open('ubuntu-12.04.1-desktop-i386.iso.torrent', 'r').read()
>>> metadata = bencode.bdecode(torrent)

A magnet hash is calculated from only the "info" section of the torrent metadata and then encoded in base32, like this:

>>> hashcontents = bencode.bencode(metadata['info'])
>>> import hashlib
>>> digest = hashlib.sha1(hashcontents).digest()
>>> import base64
>>> b32hash = base64.b32encode(digest)
>>> b32hash
'CT76LXJDDCH5LS2TUHKH6EUJ3NYKX4Y6'

You can verify that this is correct by looking here and you will see the magnet link is:

magnet:?xt=urn:btih:CT76LXJDDCH5LS2TUHKH6EUJ3NYKX4Y6

If you want to fill in some extra parameters to the magnet URI:

>>> params = {'xt': 'urn:btih:%s' % b32hash,
...           'dn': metadata['info']['name'],
...           'tr': metadata['announce'],
...           'xl': metadata['info']['length']}
>>> import urllib
>>> paramstr = urllib.urlencode(params)
>>> magneturi = 'magnet:?%s' % paramstr
>>> magneturi
'magnet:?dn=ubuntu-12.04.1-desktop-i386.iso&tr=http%3A%2F%2Ftorrent.ubuntu.com%3A6969%2Fannounce&xl=729067520&xt=urn%3Abtih%3ACT76LXJDDCH5LS2TUHKH6EUJ3NYKX4Y6'