OOP with MyTime

Akira Li 4kir4.1i at gmail.com
Wed Jul 2 21:45:28 CEST 2014


kjakupak at gmail.com writes:

> I'm trying to write a boolean function that takes two Mytime objects, t1 and t2 as arguments, and returns True if the object falls inbetween the two times.
>
> This is a question from the How to Think Like a Computer Scientist book, and I need help.
>
> What I've gotten so far:
>
> class MyTime:
>     def __init__(self, hrs=0, mins=0, secs=0):
>         self.hours = hrs
>         self.minutes = mins
>         self.seconds = secs
>     def between(t1, t2):
>         if float(t1 <= t3) and float(t3 < t2):
>             return True
>         else:
>             return False
>
> I just don't understand how to make a function that uses MyTime objects into the boolean function? Any help would be great.

A method accepts the object itself as the first parameter:

  import functools

  @functools.total_ordering
  class MyTime:
    ...
    def inbetween(self, t1, t2):
        """Return whether `self` is in [t1, t2) right-open range."""
        return t1 <= self < t2 # `self` is the object itself
    def _astuple(self):
        return (self.hours, self.minutes, self.seconds)
    def __lt__(self, other):
        """Return whether `self < other`."""
        return self._astuple() < other._astuple()
    def __eq__(self, other):
        """Return whether `self == other`."""
        return self._astuple() == other._astuple()

See
https://docs.python.org/3/library/functools.html#functools.total_ordering

Example:

  >>> MyTime(1).inbetween(MyTime(0), MyTime(2))
  True

It is equivalent to:

  >>> MyTime(0) <= MyTime(1) < MyTime(2)
  True


--
Akira




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