Re: Convert '165.0' to int

From	Grant Edwards <invalid@invalid.invalid>
Newsgroups	comp.lang.python
Subject	Re: Convert '165.0' to int
Date	2011-07-22 14:21 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<j0c11b$snt$1@reader1.panix.com> (permalink)
References	(1 earlier) <mailman.1317.1311241673.1164.python-list@python.org> <4e281f97$0$16404$426a74cc@news.free.fr> <j099fu$7kv$1@speranza.aioe.org> <19884639.rsrFWyGXb5@PointedEars.de> <j0av9t$32c$1@speranza.aioe.org>

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On 2011-07-22, Billy Mays <noway@nohow.com> wrote:
> On 7/21/2011 10:40 PM, Thomas 'PointedEars' Lahn wrote:
>> Billy Mays wrote:
>>
>>> On 07/21/2011 08:46 AM, Web Dreamer wrote:
>>>> If you do not want to use 'float()' try:
>>>>
>>>> int(x.split('.')[0])
>>>
>>> This is right.
>>
>> Assuming that the value of `x' is in the proper format, of course.  Else you
>> might easily cut to the first one to three digits of a string representation
>> (if `.' is the thousands separator of the locale, e. g.)
>
> The point (which was clear to me) was to convert a properly formatted
> string representation of a floating point number to an integer.

While that may be clear to you, that's because you've made some
assumptions.  "Convert a properly formatted string representation of a
floating point number to an integer" is not a rigorous definition.

> We might also assume the number could be a hex encoded float or be in
> scientific notation.  If the input is not properly formatted, it is 
> unreasonable for us to return a correct value.

What does "properly formatted" mean?  Who says that the character
representing the radix is "." rather than ","?

>>> Notice the last digit switched from a 3 to a 2?  Floats in python don't
>>> have arbitrary accuracy.  You would need to import decimal and use it
>>> for rounding to work properly.
>>
>> It should be floor() though, for that is what int() does.
>
> Um, what?

The example given by the OP implied that int(float(s)) did what he
wanted.  That is _not_ rounding the float.  It's the equivalent of
using the floor() function.

-- 
Grant Edwards               grant.b.edwards        Yow! Maybe we could paint
                                  at               GOLDIE HAWN a rich PRUSSIAN
                              gmail.com            BLUE --

Thread

Re: Convert '165.0' to int Leo Jay <python.leojay@gmail.com> - 2011-07-21 17:47 +0800
  Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-21 04:05 -0700
    Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-21 04:23 -0700
  Re: Convert '165.0' to int Web Dreamer <webdreamer@nospam.fr> - 2011-07-21 14:46 +0200
    Re: Convert '165.0' to int Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6@myhashismyemail.com> - 2011-07-21 09:27 -0400
      Re: Convert '165.0' to int Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-07-22 04:40 +0200
        Re: Convert '165.0' to int Billy Mays <noway@nohow.com> - 2011-07-22 00:45 -0400
          Re: Convert '165.0' to int Grant Edwards <invalid@invalid.invalid> - 2011-07-22 14:21 +0000
            Re: Convert '165.0' to int Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6@myhashismyemail.com> - 2011-07-22 10:49 -0400
              Re: Convert '165.0' to int Grant Edwards <invalid@invalid.invalid> - 2011-07-22 14:58 +0000
                Re: Convert '165.0' to int Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6@myhashismyemail.com> - 2011-07-22 11:06 -0400
                Re: Convert '165.0' to int Grant Edwards <invalid@invalid.invalid> - 2011-07-22 15:44 +0000
          Re: Convert '165.0' to int Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-07-24 10:03 +0200
      Re: Convert '165.0' to int Web Dreamer <webdreamer@nospam.fr> - 2011-07-25 10:23 +0200
        Re: Convert '165.0' to int Web Dreamer <webdreamer@nospam.fr> - 2011-07-25 11:00 +0200
    Re: Convert '165.0' to int Grant Edwards <invalid@invalid.invalid> - 2011-07-21 14:13 +0000
      Re: Convert '165.0' to int Terry Reedy <tjreedy@udel.edu> - 2011-07-21 16:00 -0400
        Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-21 22:55 -0700
          Re: Convert '165.0' to int Hrvoje Niksic <hniksic@xemacs.org> - 2011-07-22 14:42 +0200
            Re: Convert '165.0' to int rantingrick <rantingrick@gmail.com> - 2011-07-22 12:32 -0700
              Re: Convert '165.0' to int rantingrick <rantingrick@gmail.com> - 2011-07-22 12:34 -0700
              Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-23 06:06 +1000
          Re: Convert '165.0' to int Terry Reedy <tjreedy@udel.edu> - 2011-07-22 15:59 -0400
            Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-22 23:53 -0700
              Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-23 17:42 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-23 02:03 -0700
                Re: Convert '165.0' to int Billy Mays <noway@nohow.com> - 2011-07-23 11:12 -0400
                Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-24 01:20 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-23 23:53 -0700
                Re: Convert '165.0' to int Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-24 17:34 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-24 00:58 -0700
                Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-24 18:07 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-24 01:21 -0700
                Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-24 18:28 +1000
              Re: Convert '165.0' to int Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-23 18:23 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-23 02:08 -0700
              Re: Convert '165.0' to int rantingrick <rantingrick@gmail.com> - 2011-07-23 11:28 -0700
                Re: Convert '165.0' to int Billy Mays <noway@nohow.com> - 2011-07-23 23:53 -0400
                Re: Convert '165.0' to int Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-24 17:21 +1000
                Re: Convert '165.0' to int Ben Finney <ben+python@benfinney.id.au> - 2011-07-24 17:43 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-24 01:36 -0700
                Re: Convert '165.0' to int Ben Finney <ben+python@benfinney.id.au> - 2011-07-24 18:53 +1000
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-24 02:01 -0700
                Re: Convert '165.0' to int Ben Finney <ben+python@benfinney.id.au> - 2011-07-24 19:25 +1000
                Re: Convert '165.0' to int Chris Angelico <rosuav@gmail.com> - 2011-07-24 19:42 +1000
                Re: Convert '165.0' to int Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-07-25 12:04 +1200
                Re: Convert '165.0' to int Frank Millman <frank@chagford.com> - 2011-07-24 22:50 -0700
                RE: Convert '165.0' to int "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2011-08-01 20:42 -0400
                RE: Convert '165.0' to int "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2011-08-01 20:32 -0400
            Re: Convert '165.0' to int Web Dreamer <webdreamer@nospam.fr> - 2011-07-25 10:19 +0200

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