[Numpy-discussion] fromrecords yields "ValueError: invalid itemsize in generic type tuple"

[Rajat Banerjee]

Hi All,
I have been using Numpy for a while with great success. I left my
little project for a little while
(http://web.mit.edu/stardev/cluster/) and now some of my code is
broken.

I have some Numpy code to create graphs of activity on a cluster with
matplotlib. It ran just fine in July / August 2010, but has since
stopped working. I have updated numpy on my machine, I think.

In [2]: np.version.version
Out[2]: '1.5.1'

My call to np.rec.fromrecords() is throwing this exception:

File "/home/rajat/Envs/StarCluster/lib/python2.6/site-packages/numpy/core/records.py",
line 607, in fromrecords
descr = sb.dtype((record, dtype))
ValueError: invalid itemsize in generic type tuple

Here is the code with some irrelevant stuff stripped:

for line in file:
a = [datetime.strptime(parts[0], '%Y-%m-%d %H:%M:%S.%f'),
int(parts[1]), int(parts[2]), int(parts[3]), int(parts[4]),
int(parts[5]), int(parts[6]), float(parts[7])]
list.append(a)
file.close()
names = ['dt', 'hosts', 'running_jobs', 'queued_jobs',\
'slots', 'avg_duration', 'avg_wait', 'avg_load']
descriptor = {'names':
('dt,hosts,running_jobs,queued_jobs,slots,avg_duration,avg_wait,avg_load'),\
'formats' : ('S20','u','u','u','u','u','u','f')}
self.records = np.rec.fromrecords(list,','.join(names)) #used to work
#self.records = np.rec.fromrecords(list, dtype=descriptor) #new attempt

Here is one "line" from the array "list":
>>> parts (8) = ['2010-12-07 03:09:46.855712', '2', '2', '177', '2', '86', '370', '1.05'].

Neither of those np.rec.fromrecords() calls works. I've tried both
separately. They both throw the exact same exception, ValueError:
invalid itemsize in generic type tuple

Can anybody help me? Am I doing something dumb?
Thank you.
Rajat Banerjee
Masters Candidate, Computer Science, Harvard University
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[Friedrich Romstedt]

2010/12/7 Rajat Banerjee <rba...@fas.harvard.edu>:

Hi Rajat,

seems to be good that I read all email on the list, seems to be bad
that it's such a long queue.

Consider the script attached. Remarks:

* Use tuples as rows in the numpy.rec array "raw" argument. It works
for the first conversion with [] too, but I think more by incident
than by design. For the second case, which you will need, it does not
work with lists.
* Always use keyword args to fromrecords(). I believe this is a)
more error-prone b) there is no specification for positional
arguments, so their order might change (as it seems to have happened).
With positional "names", it ceases working. I don't know what it
thinks you are requesting, but for sure not "names". :-)
* Don't use the *dtype* in the way you did. I'm not authoritative
with the *dtype* arg, but at least it doesn't work this way. Use the
names= and formats= kwargs instead.

I just tinkered a bit around with your code without deep knowledge of
the numpy.rec package. I just used fromrecords() some time ago in the
way I did use it here.

Friedrich

P.S.: Please reply, if you don't I'll resend the email to you OL in
the assumtion that you desperately disappointedly unsubscribed.