Using yield while generating the sum of first 1000 prime numbers
I like using yield here and I was happy when I knew that scala has yield
def oddNumbers(xlist): for item in xlist: item += 2 xlist.append(item) yield item oddNumbers = oddNumbers([7]) primeNumbers = [2, 3, 5, 7] count = 3 summation = 17 for item in oddNumbers: isPrime = True for otherItem in primeNumbers: if item % otherItem == 0 and item != otherItem: isPrime = False if isPrime: primeNumbers.append(item) count += 1 summation += item if count == 999: break print summation
would you please explain what you are trying to achieve here?
Ahmed Soliman
13 Sep 11 at 6:35 PM
Goal is to calculate the sum of the first 1000 prime numbers:
Prime numbers are odd numbers
For any prime number it shouldn’t be divisible by any of the previous prime numbers.
Technically:
>The first function is generating the next odd number exactly like xrange except that xrange has upper limit and this one doesn’t.
>I used 2,3,5 and 7 to initialize the primesList
>I initialized oddNumbers iterator with [7] and I used it in the for loop, so it’s going to generate 9, 11, 13, ..
>Another loop, the inner loop is doing the following
>>it’s looping on the primeNums list length.
>>it’s checking if the current number isn’t divisible by all numbers then it:
>>> counts it (as we only need 1000 primes)
>>> add it to the summation
>>> add it to the primeNums list so next time it should be included in the checking process.
>>else it will change the isPrime flag to false and will skip it to the next odd number
Note: I know count =3,sum= 17, if count=999 are all magic numbers and they should be commented to let you know what I’m doing
>>3 is the start index 2->0, 3->1, 5->2, 7->3
>>17 is the summation or 2,3,5,7
>>999 is the limit
clear enough ?
me
13 Sep 11 at 10:35 PM