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.

In [3]:

fib1 = 1
fib2 = 2
fib3 = fib1

while fib2 < 10:
    print fib1
    fib3 = fib1
    fib2 += fib1
    print fib2

In [4]:

fib1 = 1
fib2 = 2

while fib2 < 10:
    fib2, fib1 = fib2 + fib1, fib2
    print fib2

In [10]:

def fib_gen(num):
    fib1 = 0
    fib2 = 1
    yield fib1
    yield fib2
    
    while fib2 < num:
        fib2, fib1 = fib2 + fib1, fib2
        yield fib2

In [16]:

[i for i in fib_gen(14)]

Out[16]:

[0, 1, 1, 2, 3, 5, 8, 13, 21]

In [15]:

sum([i for i in fib_gen(4000000) if i%2 == 0])

Out[15]:

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