I'm using PyCharm community 2018. I'm trying to find the sum of prime numbers from 1 to two million and this is my code.
primes = [x for x in range (1,2000000) if all (x%y!=0 for y in range (2,x))]
total = 0
for x in primes:
total = total + x
print (total)
It's been 20 minutes and I've still got no output. Do you have any suggestions to make it run faster or is my method wrong?
This is most likely because your method to find primes is inefficient and your range is too large.
Your algorithm is a brute force way of finding prime numbers and it's time complexity is O(n²). If you time your algorithm for smaller numbers you will see that as you increase n, time taken does not increase linearly, but is in fact quadratic.
+--------+---------------+
| n | time(in sec) |
+--------+---------------+
| 1000 | 0.007979 |
| 2000 | 0.038865 |
| 5000 | 0.137037 |
| 10000 | 0.499688 |
| 20000 | 1.892315 |
| 50000 | 10.29843 |
| 100000 | 1374.101 |
| ... | ... |
+--------+---------------+
I would suggest you to take a look at Sieve of Eratosthenes. You will find many implementations of it in whichever language you want if you search for this.