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Beginner Python Help

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  Beginner Python Help Alan Gabriel <alanunny@gmail.com> - 2016-03-18 00:04 -0700
    Re: Beginner Python Help Terry Reedy <tjreedy@udel.edu> - 2016-03-18 03:20 -0400
      Re: Beginner Python Help Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-18 09:44 +0200
    Re: Beginner Python Help Chris Warrick <kwpolska@gmail.com> - 2016-03-18 08:23 +0100
    Re: Beginner Python Help Ben Finney <ben+python@benfinney.id.au> - 2016-03-18 18:26 +1100
    Re: Beginner Python Help "Martin A. Brown" <martin@linux-ip.net> - 2016-03-18 00:50 -0700

#105183 — Beginner Python Help

Hey there,

I just started out python and I was doing a activity where im trying to find the max and min of a list of numbers i inputted.

This is my code..

num=input("Enter list of numbers")
list1=(num.split())

maxim= (max(list1))
minim= (min(list1))

print(minim, maxim)



So the problem is that when I enter numbers with an uneven amount of digits (e.g. I enter 400 20 36 85 100) I do not get 400 as the maximum nor 20 as the minimum. What have I done wrong in the code?

Thanks for the help

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#105184

On 3/18/2016 3:04 AM, Alan Gabriel wrote:
> Hey there,
>
> I just started out python and I was doing a activity
 > where im trying to find the max and min of a list of numbers i inputted.
>
> This is my code..
>
> num=input("Enter list of numbers")

input returns a string

> list1=(num.split())

list1 is a list of strings

> maxim= (max(list1))
> minim= (min(list1))

min and max compare the strings as strings, lexicographically

> print(minim, maxim)
>

> So the problem is that when I enter numbers with an uneven
> amount of digits (e.g. I enter 400 20 36 85 100)
> I do not get 400 as the maximum nor 20 as the minimum.
 > What have I done wrong in the code?

You failed to convert strings of digits to ints.  Try

list1 = map(int, num.split)

This will raise TypeError on strings that cannot be converted.

-- 
Terry Jan Reedy

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#105187

Terry Reedy writes:

> On 3/18/2016 3:04 AM, Alan Gabriel wrote:

...

>> list1=(num.split())
>
> list1 is a list of strings
>
>> maxim= (max(list1))
>> minim= (min(list1))
>
> min and max compare the strings as strings, lexicographically
>
>> print(minim, maxim)

...

> You failed to convert strings of digits to ints.  Try
>
> list1 = map(int, num.split)
>
> This will raise TypeError on strings that cannot be converted.

Written in a hurry? :)

Surely it'll raise something about a method not being iterable, and when
that is fixed, something about not being able to invent a minimum for an
empty sequence.

list1 = list(map(int, num.split()))

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#105185

On 18 Mar 2016 08:05, "Alan Gabriel" <alanunny@gmail.com> wrote:
>
> Hey there,
>
> I just started out python and I was doing a activity where im trying to
find the max and min of a list of numbers i inputted.
>
> This is my code..
>
> num=input("Enter list of numbers")
> list1=(num.split())
>
> maxim= (max(list1))
> minim= (min(list1))
>
> print(minim, maxim)
>
>
>
> So the problem is that when I enter numbers with an uneven amount of
digits (e.g. I enter 400 20 36 85 100) I do not get 400 as the maximum nor
20 as the minimum. What have I done wrong in the code?

You're dealing with strings (text) and not integers. And when comparing
strings, '1' is earlier than '2', thus '100' < '20'.

To fix this, you can use a list comprehension:

list1 = [int(i) for i in num]

You also don't need (parentheses) around functions when assigning to
variables:

maxim = max(list1)
minim = min(list1)

(Also, list1 is not a good variable name. Try something that describes its
contents.)

-- 
Chris Warrick <https://chriswarrick.com/>
Sent from my Galaxy S3.

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#105186

Alan Gabriel <alanunny@gmail.com> writes:

> I just started out python and I was doing a activity where im trying
> to find the max and min of a list of numbers i inputted.

Welcome to Python!

As a Python beginner you will be interested to join the ‘python-tutor’
forum <URL:https://mail.python.org/mailman/listinfo/tutor> which is
focussed specifically to collaborative teaching of beginner Python.

-- 
 \         “If history and science have taught us anything, it is that |
  `\     passion and desire are not the same as truth.” —E. O. Wilson, |
_o__)                                              _Consilience_, 1998 |
Ben Finney

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#105188

Greetings Alan and welcome to Python,

>I just started out python and I was doing a activity where im 
>trying to find the max and min of a list of numbers i inputted.
>
>This is my code..
>
>num=input("Enter list of numbers")
>list1=(num.split())
>
>maxim= (max(list1))
>minim= (min(list1))
>
>print(minim, maxim)
>
>So the problem is that when I enter numbers with an uneven amount 
>of digits (e.g. I enter 400 20 36 85 100) I do not get 400 as the 
>maximum nor 20 as the minimum. What have I done wrong in the code?

I will make a few points, as will probably a few others who read 
your posting.

  * [to answer your question] the builtin function called input [0]
    returns a string, but you are trying to get the min() and max() 
    of numbers; therefore you must convert your strings to numbers

    You can determine if Python thinks the variable is a string or 
    a number in two ways (the interactive prompt is a good place to
    toy with these things).  Let's look at a string:

      >>> s = '200 elephants'
      >>> type(s)                 # what type is s?
      <class 'str'>               # oh! it's a string
      >>> s                       # what's in s?
      '200 elephants'             # value in quotation marks!

   The quotation marks are your clue that this is a string, not a 
   number; in addition to seeing the type.  OK, so what about a 
   number, then?  (Of course, there are different kinds of numbers, 
   complex, real, float...but I'll stick with an integer here.)

      >>> n = 42
      >>> type(n)                 # what type is n?
      <class 'int'>               # ah, it's an int (integer)
      >>> n                       # what's in n?
      42                          # the value

  * Now, perhaps clearer?  max(['400', '20', '36', '85', '100'])
    is sorting your list of strings lexicographically instead of 
    numerically (as numbers); in the same way that the string 
    'rabbit' sorts later than 'elephant', so too does '85' sort 
    later than '400'

  * it is not illegal syntax to use parentheses as you have, but you
    are using too many in your assignment lines; I'd recommend 
    dropping that habit before you start; learn when parentheses are 
    useful (creating tuples, calling functions, clarifying 
    precedence); do not use them here:

       list1 = (num.split())  # -- extraneous and possibly confusing
       list1 = num.split()    # -- just right

  * also, there is also Tutor mailing list [1] devoted to helping 
    with Python language acquisition (discussions on this main list 
    can sometimes be more involved than many beginners wish to read)

I notice that you received several answers already, but I'll finish 
this reply and put your sample program back together for you:

  num = input("Enter list of numbers: ")
  list1 = list(map(int, num.split()))
  print(list1)
  maxim = max(list1)
  minim = min(list1)
  print(minim, maxim)

You may notice that map [2] function in there.  If you don't 
understand it, after reading the function description, I'd give you 
this example for loop that produces the same outcome.

  list1 = list()
  for n in num.split():
      list1.append(int(n))

The map function is quite useful, so it's a good one to learn early.

Good luck,

-Martin

 [0] https://docs.python.org/3/library/functions.html#input
 [1] https://mail.python.org/mailman/listinfo/tutor/
 [2] https://docs.python.org/3/library/functions.html#map

-- 
Martin A. Brown
http://linux-ip.net/

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