datetime: .datetime-.datetime = .timedelta, .time-.time=TypeError ?

Discussion in 'Python' started by Christos TZOTZIOY Georgiou, Sep 8, 2003.

  1. Is there any reason for datetime.time subtraction not returning a
    datetime.timedelta object, just like datetime.datetime subtraction does?
    It doesn't feel good having to use dumb year, month, day arguments
    constructing datetime object when doing only time arithmetic.

    If there is no specific reason apart from lack of time (no pun), I'm
    willing to research it and write a patch (I haven't seen the code, but I
    believe it would be quite easy).

    TIA
    --
    TZOTZIOY, I speak England very best,
    Microsoft Security Alert: the Matrix began as open source.
     
    Christos TZOTZIOY Georgiou, Sep 8, 2003
    #1
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  2. On Mon, 8 Sep 2003 20:57:46 -0400, rumours say that "Tim Peters"
    <> might have written:

    >[Christos TZOTZIOY Georgiou]
    >> Is there any reason for datetime.time subtraction not returning a
    >> datetime.timedelta object, just like datetime.datetime subtraction
    >> does?

    >
    >Guido didn't want time objects participating in arithmetic because the
    >desired semantics are unclear. For example, if you allow
    >
    > time1 - time2
    >
    >to return a timedelta, then you'll also want to allow
    >
    > time2 + timedelta
    >
    >to return a time, and then you've got to make up rules for what happens when
    >adding spills over a midnight boundary. Should it "wrap around"? Raise
    >OverflowError? Guido didn't want to endure arguments about that.


    So it's by design.

    [snip of the above not applying to datetime objects]

    >> It doesn't feel good having to use dumb year, month, day
    >> arguments constructing datetime object when doing only time
    >> arithmetic.

    >
    >What's wrong with using timedeltas?
    >
    >>>> print timedelta(hours=3, minutes=15) - timedelta(hours=2, minutes=45)

    >0:30:00


    A perfectly clear solution; it's just the RTFM-F [1] virus, I overlooked
    the keyword arguments...

    >> If there is no specific reason apart from lack of time (no pun), I'm
    >> willing to research it and write a patch (I haven't seen the code,
    >> but I believe it would be quite easy).

    >
    >Selling it would be harder than writing it.


    Basically, I asked for some reasoning --which you provided in the first
    paragraphs of your reply-- just in case the issue was overlooked; since
    it wasn't (and I got a solution!), I'm OK and not at all anxious to sell
    a patch :)

    Thanks.

    [1] final F standing for First
    --
    TZOTZIOY, I speak England very best,
    Microsoft Security Alert: the Matrix began as open source.
     
    Christos TZOTZIOY Georgiou, Sep 9, 2003
    #2
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  3. Christos TZOTZIOY Georgiou

    Tim Roberts Guest

    Christos "TZOTZIOY" Georgiou <> wrote:
    >--
    >TZOTZIOY, I speak England very best,
    >Microsoft Security Alert: the Matrix began as open source.


    Can you please end my suspense and explain what TZOTZIOY means? Some how,
    "Time Zone Out, Time Zone In, One Year" just doesn't cut it.
    --
    - Tim Roberts,
    Providenza & Boekelheide, Inc.
     
    Tim Roberts, Sep 11, 2003
    #3
  4. On Wed, 10 Sep 2003 21:35:30 -0700, rumours say that Tim Roberts
    <> might have written:

    >>TZOTZIOY, I speak England very best,

    >
    >Can you please end my suspense and explain what TZOTZIOY means? Some how,
    >"Time Zone Out, Time Zone In, One Year" just doesn't cut it.


    Suspense? Wow! :)

    Well, it's not an English acronym, it's just a unique word, a play on my
    last name which facilitates identifying my posts (ie Google searches,
    and DejaNews in older times). Just that.

    Earlier replies to similar questions:
    http://groups.google.com/groups?selm=
    http://groups.google.com/groups?selm=35ed5af3.11445709@147.102.222.230

    PS The Guide is useful too: http://www.bbc.co.uk/dna/h2g2/U83754 :)
    --
    TZOTZIOY, I speak England very best,
    Microsoft Security Alert: the Matrix began as open source.
     
    Christos TZOTZIOY Georgiou, Sep 13, 2003
    #4
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