Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

def Fibonacci(number):
    if number < 1:
        pass
    if number == 1:
        return  1
    if number == 2:
        return  2
    return  Fibonacci(number-1) + Fibonacci(number-2)

sum_even = 0
num = 1
while Fibonacci(num) <= 4000000:

    if Fibonacci(num) % 2 == 0:
        sum_even += Fibonacci(num)
        print 'Num count is', num,'Fibonacci is', Fibonacci(num), 'Sum is',sum_even
    else:
        print 'Num count is', num,'Fibonacci is', Fibonacci(num), 'This number is not even_value.'
    num += 1

输出：

C:\webpy\webpy\Scripts\python.exe C:/pycode/euler.py
Num count is 1 Fibonacci is 1 This number is not even_value.
Num count is 2 Fibonacci is 2 Sum is 2
Num count is 3 Fibonacci is 3 This number is not even_value.
Num count is 4 Fibonacci is 5 This number is not even_value.
Num count is 5 Fibonacci is 8 Sum is 10
Num count is 6 Fibonacci is 13 This number is not even_value.
Num count is 7 Fibonacci is 21 This number is not even_value.
Num count is 8 Fibonacci is 34 Sum is 44
Num count is 9 Fibonacci is 55 This number is not even_value.
Num count is 10 Fibonacci is 89 This number is not even_value.
Num count is 11 Fibonacci is 144 Sum is 188
Num count is 12 Fibonacci is 233 This number is not even_value.
Num count is 13 Fibonacci is 377 This number is not even_value.
Num count is 14 Fibonacci is 610 Sum is 798
Num count is 15 Fibonacci is 987 This number is not even_value.
Num count is 16 Fibonacci is 1597 This number is not even_value.
Num count is 17 Fibonacci is 2584 Sum is 3382
Num count is 18 Fibonacci is 4181 This number is not even_value.
Num count is 19 Fibonacci is 6765 This number is not even_value.
Num count is 20 Fibonacci is 10946 Sum is 14328
Num count is 21 Fibonacci is 17711 This number is not even_value.
Num count is 22 Fibonacci is 28657 This number is not even_value.
Num count is 23 Fibonacci is 46368 Sum is 60696
Num count is 24 Fibonacci is 75025 This number is not even_value.
Num count is 25 Fibonacci is 121393 This number is not even_value.
Num count is 26 Fibonacci is 196418 Sum is 257114
Num count is 27 Fibonacci is 317811 This number is not even_value.
Num count is 28 Fibonacci is 514229 This number is not even_value.
Num count is 29 Fibonacci is 832040 Sum is 1089154
Num count is 30 Fibonacci is 1346269 This number is not even_value.
Num count is 31 Fibonacci is 2178309 This number is not even_value.
Num count is 32 Fibonacci is 3524578 Sum is 4613732

Process finished with exit code 0