Custom Query (121 matches)

Reported by edemaine@…, 7 years ago.

Here are two simple wall-clock timings comparing PyYAML to PySyck on a Pentium 4 2.8GHz with 1MB cache and 1GB RAM:

$ wc file1.yaml
 2036  8767 59154 file1
$ test.py file1.yaml
0:00:00.001419 to read the YAML via Syck
0:00:04.029627 to read the YAML via PyYAML
$ wc file2.yaml
  8949  35105 317342 file2
$ test.py file2.yaml
0:00:00.001564 to read the YAML via Syck
0:00:19.288912 to read the YAML via PyYAML

I do not expect PyYAML to be terribly competitive with Syck: the language barrier is big, and PyYAML is written with a higher level of abstraction. But I was surprised to see a factor of 12,000 difference. I wonder if a bit of profiling and tuning might reduce this gap to just a couple of orders of magnitude (100x) instead of four? Personally, 19 seconds to read a 0.3 meg file is too slow for my application, so I'll have to switch back to Syck for now, unfortunately. Just food for thought...

Reported by edemaine@…, 7 years ago.

Example:

>>> import yaml, datetime
>>> yaml.dump(datetime.datetime(2005, 7, 8, 17, 35, 4, 517600))
'2005-07-08 17:35:04.517600\n'
>>> yaml.load(_)
datetime.datetime(2005, 7, 8, 17, 35, 4, 517599)

This breaks the desired rule that yaml.load(yaml.dump(x)) == x in a case where there should be no roundoff. (datetime.datetime uses integers everywhere to avoid any error.)

The offending code seems to be line 321 in yaml/constructor.py:

fraction = int(float(values['fraction'])*1000000)

This seems to be an "easy" way to convert the trailing '.517600' into an integer, but it can go beyond floating-point precision. Wouldn't the following work?

fraction = int(values['fraction'][:6].ljust(6, '0'))

Reported by edemaine@…, 7 years ago.

Could you compile a Windows binary of PyYAML for Python 2.5 (released fairly recently)? Ideally with libyaml support built in...