Floating point calculation problem

From	"Schizoid Man" <schiz_man@21stcentury.com>
Newsgroups	comp.lang.python
Subject	Floating point calculation problem
Date	2013-02-02 10:27 +0000
Organization	A noiseless patient Spider
Message-ID	<keipl5$kif$1@dont-email.me> (permalink)

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I have a program that performs some calculations that runs perfectly on 
Python 2.7.3. However, when I try to execute it on Python 3.3.0 I get the 
following error:
    numer = math.log(s)
TypeError: a float is required

The quantity s is input with the following line: s = input("Enter s:   ")

To get rid of the compile error, I can cast this as a float: s = 
float(input("Enter s:   "))

However, then the result returned by the method is wrong. Why does this 
error occur in version 3.3.0 but not in 2.7.3? Why is the result incorrect 
when s is cast as a float (the casting is not required in 2.7.3)? How is 
Python dynamically typed if I need to cast (in version 3.3.0 at least) to 
get rid of the compile error?

Thanks in advance.

PS - I'm a Python newbie.

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Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 10:27 +0000
  Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 21:34 +1100
    Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:14 +0000
      Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:20 +1100
        Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:34 +0000
          Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:38 +1100
            Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:51 +0000
              Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-02 22:58 +1100
                Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 15:48 +0000
                Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 15:54 +0000
                Re: Floating point calculation problem Chris Angelico <rosuav@gmail.com> - 2013-02-03 03:00 +1100
                Re: Floating point calculation problem Michael Torrie <torriem@gmail.com> - 2013-02-02 11:19 -0700
                Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-03 12:25 +1100
                Re: Floating point calculation problem Dave Angel <d@davea.name> - 2013-02-02 21:20 -0500
                Re: Floating point calculation problem Michael Torrie <torriem@gmail.com> - 2013-02-02 21:22 -0700
              Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 23:11 +1100
      Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 22:45 +1100
        Re: Floating point calculation problem "Schizoid Man" <schiz_man@21stcentury.com> - 2013-02-02 11:50 +0000
  Re: Floating point calculation problem Chris Rebert <clp2@rebertia.com> - 2013-02-02 02:47 -0800
  Re: Floating point calculation problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-02 23:05 +1100

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