Question

Having trouble with problem set 1, problem 1:
I have a program that calculates every odd number, through a 'while' loop. I can do a conditional test to check if each number generated is divisible by 3, 5, 7, etc. but I can't make it so that a new test is added each time a new number is printed:
x=0
x=x+1
n=1
while n<1000:
x=x+2
if x%3!=0 or x==3:
print (x)
n=n+1
How can I make it so that each time a number is printed, that number gets added to a list of tests that will be done on the next iteration of the loop? Help!

Answer 1

I don't know exactly which course this is from, and I don't know if you have studied methods yet. For that matter, I don't know if you have studied tuples or lists yet either.

However, assuming that the easiest of these is a tuple, I will try to help you with this problem.

Every time you find a prime number, you can add it to your tuple. So for this first ten numbers your tuples would look like this:
1: (,)
2: (2,)
3: (2,3)
4: (2, 3)
5: (2, 3, 5)
6: (2, 3, 5)
7: (2, 3, 5, 7)
8: (2, 3, 5, 7)
9: (2, 3, 5, 7)
10: (2, 3, 5, 7)

Now, in python, you can iterate over elements of a tuple. Something like:
for prime in primesTuple:
test divisibility

Hopefully this helps a little bit without giving it away.

Answer 2

Tuples are immutable (unchangeable). Lists are mutable. If you're going to be adding to it, a list is more suitable. You can fake adding to a tuple, but you're actually creating a new tuple with the elements of your old tuple and what you added.

Answer 3

Absolutely true, but tuples are often introduced first in CS courses, and I wanted to keep it as likely as possible that he could follow me.

Answer 4

Let me rephrase, in my CS intro course, tuples were introduced first.

Answer 5

actually ye for that assignment list arent yet taught...so i suppose tuples it should be:).

Answer 6

Just to clarify (I'm new to OpenStudy, so I don't know who's on this site or how it works), I'm going through the MIT 6.00 Intro to CS videos

Answer 7

Also, thank you very much to everyone. I think I'm close. However, there's one crucial part that is missing:

primeTuple= (2,)
x=0
n=1
x=x+1
while n<300:
x=x+2
for test in primeTuple:
if x%test!=0 or x==test:
print (x)
newTuple=(x,)
primeTuple= primeTuple+newTuple
n=n+1
What is happening now is that when I run it, each number is printed as many times as there are tests. So 3 is printed once, 5 twice (not divisible by two: print. not divisible by 3: print), 7 three times, and so on. How do I make it so that the condition to print x is that x not be divisible by any and all of the numbers?

Answer 8

ok so:
1. x=0,x=x+1
why not directly x=1 ? no point doing that.

2.(not a mistake just a python way to write it) x=x+2 u can write it x+=2.

3.to get your primeTuple printed you have to put a print statement in the end that asks the code to print primeTuple.

4. x==test
i dont think you need it since your x is always bigger than your test.(recheck that maybe im wrong (its 22:00 for me bit sleepy xD)

5.(again not wrong but tidier)
newTuple=(x,)
primeTuple= primeTuple+newTuple

you can write this as:

primeTuple+=(x,)

6.now your problem is that
a. your code prints all odds!
b.it print them multiple times.

solution hint:
*set a Boolean controll variable to some state( usually True)
*in your for loop, control if, for some condition this variable should stay True or change to False....
**if False get out of the loop....
**if True : add x to primeTuple and n+=1

hope this helps!if you need more help ask so:)

Answer 9

Thank you for your help, I figured it out! Very proud of myself. The code I ended up with might be a little cluttered, but it was my first, and it got the job done:

primeTuple= (2,)
tupleNumber=1
x=1
n=1
while n<1000:
x+=2
testNumber=0
for test in primeTuple:
if x%test!=0 or x==test:
testNumber+=1
if tupleNumber==testNumber: #this makes it so all the tests are run
#before the x prints
print (x)
primeTuple+= (x,)
tupleNumber+=1
n+=1
primeTuple+= (x,)
tupleNumber+=1
n+=1

Answer 10

well ull learn to write "cleaner" codes...we all will! mine are not a lot better but im learning!
good job for the code!:)