Improving a few Project Euler solutions.

I did about a dozen Project Euler about this time last year. Since then, I've revisited several of my solutions to see if and how I could improve a couple of them based on what I've learned since then.

Euler #2

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.

Original Solution:

a, b = 1, 0

total = 0

while True:
    x = a+b
    if x > 4000000:
        break

    if (x %2) == 0:
        total += x

    a,b = a+b, a

New Solution

from itertools import takewhile
def fibs():
    a,b = 1,0
    while True:
        yield a+b
        a,b = a+b,a

nums = takewhile(lambda x: x<4000000, fibs())
total = sum(n for n in nums if not n%2)

Euler #8

The four adjacent digits in the 1000-digit number that have the greatest product are 9 * 9 * 8 * 9 = 5832.

73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

Old Solution:

from functools import reduce
nums = [int(x) for x in ...]

limit = 13
run = []
largest = 0

while n:
    run.insert(0, n.pop())
    if len(run) > limit:
        run.pop()

    x = reduce(lambda x,y: x*y, run)
    if x > largest:
        largest = x

New Solution:

from functools import reduce
from operator import mul
from collections import deque

nums = [int(x) for x in ...]
run = deque(maxlen=13)

for n in nums:
    run.append(n)
    x = reduce(mul, run)
    largest = x if x > largest else largest

Opinion?

When I wrote the original solutions to this problems, I wasn't very familiar with Python (honestly, I'm still not). I only knew about collections and itertools and functools as things that existed. But they intimidated me. I took on Project Euler (briefly) as an excuse to learn Python. However, I can see that while I learned how I could solve problems in Python, I didn't learn about Python itself.

By utilizing libraries like collections and functools and itertools, Solution #2 goes from 9 lines (not counting spacing lines) to 8 lines which includes an import and a function definition; Solution #8 goes from 12 lines to 9 -- including three imports. These may not be greatest space savers in all of time, but they add up. Imagine saving two or three lines of code in every class, function or module you write?

You can see there's a lot of overthinking and logic that's removed by using something like deque instead of trimming a list down manually. It's faster to run and more importantly, it's faster to write, read and maintain.