[Matplotlib-users] Crude but possibly useful little hack

[Kenneth M. <kmm...@wi...>]

I've been using matplotlib for some plotting involving dated
values, but wasn't able to figure out how to use the new
plot_date with log axes. (I'm still a rank newbie at matplotlib.)
It struck me that an integer that "knew" it represented
seconds since the epoch would be a neat way of feeding
matplotlib's non-date functions the values they expected,
while at the same time manipulating dates in my own code;
and, since I'd just done a bit of reading of new-style classes
in Python, came up with the following:


import datetime, time

class intdate(int):
     '''Subclasses int for use as dates.'''
     def __init__(self, ordinal):
         int.__init__(self, ordinal)
         self.__date = datetime.date.fromtimestamp(ordinal)

     day = property(fget=lambda self:self.__date.day)
     month = property(fget=lambda self:self.__date.month)
     year = property(fget=lambda self:self.__date.year)

     def isoformat(self): return self.__date.isoformat()

     def timetuple(self): return self.__date.timetuple()

     def date(self): return self.__date

def epoch(x):
     'convert userland datetime instance x to epoch'
     return time.mktime(x.timetuple())

def date(year, month, day):
     return intdate(epoch(datetime.date(year, month, day)))

def today():
     return intdate(epoch(datetime.date.today()))


Use 'today' and 'date' to create intdate instances. They
can be used in python wherever you would normally
use an integer (I believe), but can also be treated as
instances of the intdate class. They can't be used in
numarry/numeric of course, and certainly aren't suited
for use with large data sets, but I thought this was sorta
neat, in a nasty hacky kind of way. You could of course
expand the indate class; my needs were simple. It
would also be simple to reimplement some of the functions
so an internal instance of datetime wasn't necessary...

Too bad there isn't a standard C primitive type for representing
dates in some standardized numeric format, such as the epoch
style. But I thought some people might find this useful and/or
informative

Cheers,
Ken