Check if this basic Python script is coded right

[Terry Reedy]

On 10/26/2013 1:36 PM, HC wrote:
> I'm doing my first year in university and I need help with this basic assignment.
>
> Assignment: Write Python script that prints sum of cubes of numbers between 0-200 that are multiples of 3. 3^3+6^3+9^3+12^3....+198^3=?
>
> My script:
> count = 0
> answer = 0
>
> while count<200:
>      if count%3==0:
>          answer = answer + count**3
>      count = count + 1
>
> print ("Result is: " +str(answer))
>
> Is it all okay?

Generalize the problem, put the code in a reusable testable function, 
and start with test cases.
--
def sum33(n):
   "Return sum of cubes of multiples of 3 <= n."

for n, sm in ( (0,0), (2,0), (3,27), (4,27), (6,243), ):
   assert sum33(n) == sm

print(sum33(200))
--
This will fail because None != 0. Now add 'return 0' and the first two 
cases pass and then it fails with None != 27. Now change 'return 0' to

   answer = 0
   for i in range(3, n+1, 3):
     answer += i*i*i
   return answer

and it will print 131990067, which I presume is correct. Putting your 
code in the body instead, indented, with '200' replaced with 'n+1', and 
with 'return answer' added, gives the same result after passing the same 
tests.

-- 
Terry Jan Reedy