Learning Python with Project Euler: Problem 2

This is another short problem in Project Euler. The problem states:

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

So, we need to know what the Fibonacci sequence is. The first two numbers in the sequence are 1 and 1. After that, the next number is the sum of the previous two numbers.  Mathematically, we can define this sequence by:  F(n)=F(n-1)+F(n-2), F(0) = 1, F(1) = 1

Below is my Python implementation.  I use a tuple, bitwise and operation, Python's ability to assign multiple variables on the same line.

# only persist the last 2 values of the sequence
vsum, fib_nums = 0, (1, 1)
while fib_nums[0] < 4000000:
  # shift the 2nd value to the 1st position, add the previous 2 values and set
  # it at the 2nd position
  fib_nums = (fib_nums[1], fib_nums[0] + fib_nums[1])
 
  # only add latest fib number if it is even; using bitwise operations we can
  # tell if a number is even or odd by checking the last bit
  if fib_nums[1] & 1 == 0: vsum += fib_nums[1]

print 'sum: ' + str(vsum)