Project Euler #40

euler40.py

from operator import mul
from itertools import takewhile

def nth():
    i = 1
    s = '1'
    while 1:
        yield i, s[i - 1]
        i += 1
        s += str(i)

print reduce(mul,
                (int(c) for (i, c) in
                    (takewhile(lambda(i, c): i <= 1000000, nth()))
                        if i in (1, 10, 100, 1000, 10000, 100000, 1000000)))