Beginner Python Help
Martin A. Brown
martin at linux-ip.net
Fri Mar 18 03:50:38 EDT 2016
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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