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Re: How do I calculate a mean with python?

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On 16Sep2013 16:33, William Bryant <gogobebe2@gmail.com> wrote:
| Hey I am new to python so go easy, but I wanted to know how to make a program that calculates the maen.
| 
| List = [15, 6, 6, 7, 8, 9, 40]
| def mean():
|     global themean, thesum
|     for i in List:
|         thecount = List.count(i)
|         thesum = sum(List)
|     themean = thesum / thecount
| 
| Why doesn't this work?

Well:

  - always include the output you get from your program, and say
    why you think it is incorrect

  - just style: we tend to name variables in lower case in Python, and
    classes with an upper case letter; "List" is a bit odd (but
    "list" is taken; how about "values"?)

  - more than style: WHY are you using global variables; just return the mean
    from the function!

  - teh variable "List" inside the function is _local_; your function does not
    accept a parameter

  - sum(List) sums the whole list
    you run it many times
    why?

  - what do you think "count()" does?

  - you should print i, thecount and thesum on each iteration of
    the list; it will help you see what your function is doing, and
    therefore to figure out what it is doing wrong

I would write a mean like this:

    def mean(values):
      return sum(values) / len(values)

There are circumstances where that is simplistic, but it is the classic
definition of the mean.

Cheers,
-- 
Cameron Simpson <cs@zip.com.au>

Microsoft Mail: as far from RFC-822 as you can get and still pretend to care.
      - Abby Franquemont-Guillory <abbyfg@tezcat.com>

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Thread

How do I calculate a mean with python? William Bryant <gogobebe2@gmail.com> - 2013-09-16 16:33 -0700
  Re: How do I calculate a mean with python? Jugurtha Hadjar <jugurtha.hadjar@gmail.com> - 2013-09-17 00:52 +0100
  Re: How do I calculate a mean with python? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-16 23:55 +0000
  Re: How do I calculate a mean with python? MRAB <python@mrabarnett.plus.com> - 2013-09-17 01:01 +0100
  Re: How do I calculate a mean with python? Jugurtha Hadjar <jugurtha.hadjar@gmail.com> - 2013-09-17 01:08 +0100
  Re: How do I calculate a mean with python? Cameron Simpson <cs@zip.com.au> - 2013-09-17 09:59 +1000
  Re: How do I calculate a mean with python? Dave Angel <davea@davea.name> - 2013-09-17 00:50 +0000
  Re: How do I calculate a mean with python? Travis Griggs <travisgriggs@gmail.com> - 2013-09-17 08:25 -0700
  Re: How do I calculate a mean with python? William Bryant <gogobebe2@gmail.com> - 2013-09-17 12:44 -0700
  Re: How do I calculate a mean with python? William Bryant <gogobebe2@gmail.com> - 2013-09-17 12:45 -0700
  Re: How do I calculate a mean with python? William Bryant <gogobebe2@gmail.com> - 2013-09-17 13:10 -0700
    Re: How do I calculate a mean with python? Joel Goldstick <joel.goldstick@gmail.com> - 2013-09-17 17:02 -0400
    Re: How do I calculate a mean with python? MRAB <python@mrabarnett.plus.com> - 2013-09-17 22:26 +0100
      Re: How do I calculate a mean with python? William Bryant <gogobebe2@gmail.com> - 2013-09-17 14:31 -0700
        Re: How do I calculate a mean with python? Joel Goldstick <joel.goldstick@gmail.com> - 2013-09-17 19:49 -0400
  Re: How do I calculate a mean with python? Bryan Britten <britten.bryan@gmail.com> - 2013-09-17 18:53 -0700

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