def p2(lt=4000000, fltr=lambda x: x % 2 == 0):
"""P2: By considering the terms in the Fibonacci sequence whose
values do not exceed four million, find the sum of the even-valued
terms.
"""
fg = nttools.gen_fib()
# filter and sum even elements of fibonacci series up to value 'lt'
return reduce(op.add, filter(fltr, takewhile(lambda x: x < lt, fg)))
def p25():
for i, n in enumerate(nttools.gen_fib()):
if len(str(n)) >= 1000:
return (i, n)