Ticket #30 (closed defect: fixed)

Opened 3 years ago

Last modified 3 years ago

Timestamp support has floating-point roundoff

Reported by: edemaine@mit.edu Assigned to: xi
Priority: normal Component: pyyaml
Severity: normal Keywords:
Cc:

Description

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'))

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Change History

10/04/06 03:54:57 changed by xi

  • status changed from new to closed.
  • resolution set to fixed.

Fixed in [234].

Thanks for the patch, it works perfectly.

Add/Change #30 (Timestamp support has floating-point roundoff)




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