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The code below checks whether a given integer can be expressed by the sum of two primes:
def sum_of_primes(num):
isPrime = 1
for i in range (2,int(num/2),1):
if(num % i == 0):
isPrime = 0
break
return isPrime
num = int(input("Enter a number : "))
flag = 0
i = 2
for i in range (2,int(num/2),1):
if(sum_of_primes(i) == 1):
if(sum_of_primes(num-i) == 1):
print(num,"pode ser expresso como a soma de",i,"e",num-i)
flag = 1;
if (flag == 0):
print(num,"não pode ser expresso como a soma de dois primos")
the code works correctly (except when I enter the number 5. It says that it cannot be formed by the sum of two primes but we know that it can: 2+3. I haven’t figured out why).
What I need to do is adapt the code so that it receives a list of numbers and does this check in the typed list. I used the following input:
num = [int(n) for n in input("Digite os número: ").split()]
However I did not get the expected result, IE, the program does not check for all items of the typed list.
Can someone help me?
range(2,int(num/2),1)- whennumis 5,int(num / 2)is 2, so you created arange(2,2,1), only in a range the final value is not included, so it does not even enter thefor. Just switch torange(2,int(num/2) + 1)- note also that you do not need the third parameter, because its default value is already 1– hkotsubo
The famous Goldbach conjecture says that every PAR number greater than 3 equals the sum of two prime numbers.
– Solkarped
perfect with respect to the range: now works with the 5.
– StatsPy
Now I just need to be able to do the same check when the user type a list instead of a single number.
– StatsPy
If you already have a function that verifies that a certain number can be formed by two primes, then you can do another function that scrolls through the numbers in the list and calls the function to verify sum of primes one by one.
– Anthony Accioly
The body of this new function can be something as trivial as
all(is_sum_of_primes(n) for n in lista)– Anthony Accioly