As a first piece of non-trivial Python programming I coded up an equivalent framework in Python 2.5, available here. The framework allows you to set up a class with bitemporal properties that track the history and evolution of the value assigned to those properties. Here's a small example that should give you a feel for what you can do:
from bitemporal import *
class Person:
def __init__(self, name):
self.name = name
self.address = BitemporalProperty()
p = Person("John Doe");
p.address.assign("Smallville", Interval(date(1975, 4, 3), date.max))
p.address.assign("Bigtown", Interval(date(1994, 8, 26), date.max))
print p.address.now() # Bigtown
print p.address.on(date(1980, 1, 1)) # Smallville
I'm looking for feedback on this code, which right now is only about 300 lines long. Is this code pythonic? Or is this Java-style Python code? If so, what areas need to be improved? Personally, I have doubts about at least a few things:
- The type checks in the TimeFrame class (and a few other classes) feel iffy:
@classmethod def set_reference(cls, value): if type(value) == date: cls.reference = datetime.combine(value, time()) else: cls.reference = value
But how else do I ensure that a timeframe always holds a datetime?
- The BitemporalWrapper class feels Java-like. It decorates another object with bitemporal information and functionality. Is there a better way to do this in a dynamically typed language?
- I considered using @property for the assign() method on the BitemporalProperty class, but the problem is that you often want to pass in a validity interval, which rules out use of "=".
