Re: [Tutor] please help me modify this code so that I can utilize raw_input

[Oscar Benjamin]

On 4 October 2016 at 19:11, Alan Gauld via Tutor  wrote:
>> """Define a function sum() and a function multiply() that sums and
>> multiplies (respectively) all the numbers in a list of numbers. For
>> example, sum([1, 2, 3, 4]) should return 10, and multiply([1, 2, 3, 4])
>> should return 24."""
>
> 
> I do wish teachers would not ask students to reinvent the wheel.

You may be misunderstanding the teacher's objectives here. Sometimes
Python is used to introduce the concept of programming more generally
rather than specifically to prepare someone for professional
programming using Python. I don't know about you but I came to Python
after a number of other programming languages. Now that I teach
programming I can see that it's important in a first programming
introduction to cover nuts and bolts type algorithmic thinking. sum()
is a good example of an algorithm that most people are already used to
performing on pen and paper making it a good candidate for learning to
use loops and functions.

> Python already has a perfectly good sum() function.

Writing your own sum function helps to understand what actually
happens when using the standard sum function. I do the same thing with
my students in C teaching them how to make their own e.g. strlen
function. I will tell them that strlen exists afterwards but I want
them to understand what the null byte is and writing your own (or just
looking at a) strlen implementation helps with that. Likewise simply
using a function e.g. strcat without understanding its implementation
can lead to segfaults so there can be a relevance in understanding the
implementation even if you don't intend to reimplement something in
your own code. The implications of the implementation of sum are also
non-trivial which is why the stdlib contains at least 3 different sum
functions.

It's great that Python comes with so many functions to do common
tasks. However from personal experience teaching Python as a first
language can lead to the disadvantage that many students become spoilt
programmers. They will learn to assume that there is a function for
exactly what they want and all they ever need to do is ask a precise
question in a search engine and read the first stackoverflow page.
That may be the correct approach for many problems but it isn't
always. A programmer should have the ability to implement basic
algorithms (e.g. sum) for themselves when necessary.

> And both problems become trivial if using functools.reduce()
> 

Different people think in different ways but I reckon most people -
and especially most beginners - would find a loop more straightforward
than reduce. I doubt that the OP is at a stage where using reduce
seems trivial.

--
Oscar
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Re: [Tutor] please help me modify this code so that I can utilize raw_input

[Alan Gauld via Tutor]

On 04/10/16 15:04, Richard Koeman wrote:
> I would like to modify this code so that instead of me calling the function
> with the list as shown [1,2,3,4], the user inputs the list with raw_input.
> 

You don't need to modify your code you just need ton write a function
that reads a list from the user. Notice that this can e done by either
repeatedly asking the user to input values until they are done or by
reading a string containing the values and converting the string to a
list of numbers.


> """Define a function sum() and a function multiply() that sums and
> multiplies (respectively) all the numbers in a list of numbers. For
> example, sum([1, 2, 3, 4]) should return 10, and multiply([1, 2, 3, 4])
> should return 24."""


I do wish teachers would not ask students to reinvent the wheel.
Python already has a perfectly good sum() function.
And both problems become trivial if using functools.reduce()


> 
> def sum(mylist = [], *args):
>   print mylist
>   sum_of_number = 0
>   for i in mylist:
> sum_of_number += i
>   print "The sum of the digits in your number is %s" %(sum_of_number)

> def multiply(mylist = [], *args):
>   product_of_number = 1
>   for i in mylist:
> product_of_number = product_of_number * i
>   print "The product of the digits in your number is %s"
> %(product_of_number)
> 
> sum([1,2,3,4])
> multiply([1,2,3,4])

Incidentally, notice that the assignment asks you to *return* the
results not print them. This is good practice, keep the printing
separate from the calculation. You can then print the result,
if you wish, with

print( sum([]) )

hth
-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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[Tutor] please help me modify this code so that I can utilize raw_input

[Richard Koeman]

I would like to modify this code so that instead of me calling the function
with the list as shown [1,2,3,4], the user inputs the list with raw_input.

Thanks in advance


"""Define a function sum() and a function multiply() that sums and
multiplies (respectively) all the numbers in a list of numbers. For
example, sum([1, 2, 3, 4]) should return 10, and multiply([1, 2, 3, 4])
should return 24."""

def sum(mylist = [], *args):
  print mylist
  sum_of_number = 0
  for i in mylist:
sum_of_number += i
  print "The sum of the digits in your number is %s" %(sum_of_number)
def multiply(mylist = [], *args):
  product_of_number = 1
  for i in mylist:
product_of_number = product_of_number * i
  print "The product of the digits in your number is %s"
%(product_of_number)

sum([1,2,3,4])
multiply([1,2,3,4])

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