Question

Possible Duplicate:
Python program to find fibonacci series. More Pythonic way.

Hey, i was trying to write a script which sums all the even terms in “Fibonacci Sequence” under 4 millions.

Fibonacci1 = 1
Fibonacci2 = 2
a = 2
i = 4
for i in range(1,4000000):
 Fibonacci1 = Fibonacci1 + Fibonacci2
 if Fibonacci1 % 2 == 0:
  a = a + Fibonacci1
 Fibonacci2 = Fibonacci1 + Fibonacci2
 if Fibonacci2 % 2 == 0:
  a = a + Fibonacci2
print a
raw_input()

it should takes less than a minute, but it took all night and it wasn’t solved !

---

Edit: Sorry guys, i misunderstood the problem. I though it means that i have to sum all the even terms UP TO 4 million ! But the solution was to sum all the even terms UNTIL 4 million.

Working code (finished in less than one second):

Fibonacci1 = 1
Fibonacci2 = 2
a = 2
while a < 4000000:
 Fibonacci1 = Fibonacci1 + Fibonacci2
 if Fibonacci1 % 2 == 0:
  a = a + Fibonacci1
 Fibonacci2 = Fibonacci1 + Fibonacci2
 if Fibonacci2 % 2 == 0:
  a = a + Fibonacci2
print a
raw_input()

Answer 1

The loop condition is wrong, it should be something like this:

while True:
    Fibonacci1 = Fibonacci1 + Fibonacci2
    if Fibonacci1 % 2 == 0:
        if a + Fibonacci1 > 4000000:
            break
        a = a + Fibonacci1
    Fibonacci2 = Fibonacci1 + Fibonacci2
    if Fibonacci2 % 2 == 0:
        if a + Fibonacci2 > 4000000:
            break
        a = a + Fibonacci2