Better support the "limit" parameter

[GoogleCodeExporter]

The "limit" parameter of the various methods is currently not properly 
supported. The attached patch changes this and vastly simplifies the data 
processing.

Before:

assert len(user.get_loved_tracks(limit=30)) == 30
-> Fine
assert len(user.get_loved_tracks(limit=100)) == 60
-> Fine
assert len(user.get_loved_tracks(limit=None)) == 60
-> AssertionError
assert len(user.get_loved_tracks(limit=0)) == 60
-> AssertionError

After:

assert len(user.get_loved_tracks(limit=30)) == 30
-> Fine
assert len(user.get_loved_tracks(limit=100)) == 60
-> Fine
assert len(user.get_loved_tracks(limit=None)) == 60
-> Fine
assert len(user.get_loved_tracks(limit=0)) == 60
-> Fine

Original issue reported on code.google.com by matsusuk...@gmail.com on 19 Mar 2011 at 8:37

Attachments:

• pylast_collect_nodes.patch

[GoogleCodeExporter]

It seems like this version won’t work with Libre.fm since passing 0 as limit 
yields an empty tracklist. The only workaround to get it working on both is 
using an insanely huge number as limit.

In any case, the current version of the _collect_nodes() function should 
support None as value for limit to indicate unlimited data retrieval.

Original comment by matsusuk...@gmail.com on 19 Mar 2011 at 10:42

[GoogleCodeExporter]

Unfortunately this patch doesn't work for large value of limit. Lastfm returns 
error for limit=4000:

XML Parsing Error: no element found
Location: 
http://ws.audioscrobbler.com/2.0/?method=library.gettracks&api_key=b25b959554ed7
6058ac220b7b2e0a026&limit=4000&user=joanofarctan
Line Number 29787, Column 45:    <name>Psychometry III (Break 3000 Remix)
--------------------------------------------^

and in python:

>>> len(lib.get_tracks(limit=2000))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pylast.py", line 2030, in get_tracks
    for node in _collect_nodes(limit, self, "library.getTracks", True, params):
  File "pylast.py", line 3511, in _collect_nodes
    doc = sender._request(method_name, cacheable, params)
  File "pylast.py", line 970, in _request
    return _Request(self.network, method_name, params).execute(cacheable)
  File "pylast.py", line 828, in execute
    response = self._download_response()
  File "pylast.py", line 819, in _download_response
    self._check_response_for_errors(response_text)
  File "pylast.py", line 838, in _check_response_for_errors
    raise MalformedResponseError(self.network, e)
pylast.MalformedResponseError: Malformed response from Last.fm. Underlying 
error: no element found: line 37702, column 33

Resolution from issue 63 works:
>>> len(lib.get_tracks(limit=2000))
2000
>>> len(lib.get_tracks(limit=None))
6045

I think that it's not possible to avoid using 'page' paremeter for large values 
of 'limit' parameter.

Original comment by grzegorz...@gmail.com on 20 Mar 2011 at 8:47

[GoogleCodeExporter]

Yes, I can confirm that the suggested fix in issue 63 works fine as well 
without breaking compatibility with Libre.fm. Ignore my suggestion then and go 
with that one instead. :-)

Original comment by matsusuk...@gmail.com on 20 Mar 2011 at 11:51

[GoogleCodeExporter]

I've implemented this in my fork:
https://github.com/hugovk/pylast/issues/66

Original comment by hugovk@gmail.com on 17 Apr 2014 at 1:52