[egenix-users] Matplotlib (pylab) datetime incompatible with Egenix mxDateTime

[M.-A. Lemburg]

Simon Hook wrote:
> Hi,
> 
> [cross posted to egenix and matplotlib]
> 
> I have been using the egenix mxDateTime module and want to plot some of
> the dates with Matplotlib (pylab). Pylab uses num2date and date2num to
> covert datesandtimes to floating point values for plotting.
> Unfortunately if you give pylab date2num an egenix DateTime object,
> pylab bombs. Is there a simple way to use egenix DateTime objects with
> Pylab?
> 
> Below is a simple example
> 
> #D:\apps\Python23\python.exe
> 
> from datetime import *
> from mx.DateTime import *
> from pylab import *
> 
> # This works
> a=datetime(2005,10,10,5,5,5)
> print a
> 
> # This works
> b=DateTime(2005,10,10,5,5,5)
> print b
> 
> # This works
> c=date2num(a)
> print c
> 
> # This fails
> d=date2num(b)
> print d
> 
> The output and failure message is:
> 
> 2005-10-10 05:05:05
> 2005-10-10 05:05:05.00
> 732229.211863

I'm not sure what date2num() uses as epoch, but it looks like
some variant of a Julian Day Number:

>>> b.jdn
2453653.711863426
>>> b.tjd
3653.2118634259259

> Traceback (most recent call last):
>  File "datetime-problem.py", line 20, in ?
>    d=date2num(b)
>  File "D:\apps\Python23\lib\site-packages\matplotlib\dates.py", line
> 174, in da
> te2num
>    if not iterable(d): return _to_ordinalf(d)
>  File "D:\apps\Python23\lib\site-packages\matplotlib\dates.py", line
> 137, in _t
> o_ordinalf
>    base =  dt.toordinal()
> AttributeError: toordinal

.toordinal() is a datetime method which is not supported by mxDateTime
instances.

-- 
Marc-Andre Lemburg
eGenix.com

Professional Python Services directly from the Source  (#1, Jul 16 2006)
>>> Python/Zope Consulting and Support ...        http://www.egenix.com/
>>> mxODBC.Zope.Database.Adapter ...             http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
________________________________________________________________________

::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! ::::