python 3.x - Finding the sum of primes below 10 -

>>> k=1 >>> sum=0 >>> in range (2,10):         j in range (2,i):             if ((i%j)==0):                 k=0     if (k==1):         sum+=i   >>> print(sum)     5 

i don't know why, code, instead of giving 17 output, gives 5.

you need set k flag 1 each time for i loop moves next number:

for in range (2,10):     k = 1     j in range (2,i):         if ((i%j)==0):             k=0     if (k==1):         sum+=i 

without doing code ever finds 5 prime number, , ignores after that.

note in python, 0 considered false when used in boolean context (such if statement), 1 true, can use if k:. better still, use true , false , better variable names, such is_prime rather k. can drop lot of parentheses:

sum = 0 num in range (2, 10):     is_prime = true     in range (2, int(num ** 0.5) + 1):         if not num % i:             is_prime = false     if is_prime:         sum += num 

i made use of fact need check square root of number see if there divisors, cutting loops down significantly.

last not least, can make use of for ... else construct; if use break in for loop, else branch never gets executed, if for loop completes end without breaking out, is; removes need boolean flag:

sum = 0 num in range (2, 10):     in range (2, int(num ** 0.5) + 1):         if not num % i:             break     else:         sum += num