• Place import names at top of script

I am sure you know if you copy paste your code into a console as is, it will raise NameErrors.

Put the following:

from functools import reduce
from itertools import islice
from math import prod

At the top of script.

Your second function is actually quite effictive, but not as effictive as it can be, you made a simple mistake, max can return the maximum value of more than two numbers, its arguments can be infinitely many or an iterable.

So it should be written as this:

def greatest_product(s):
    return max(prod(map(int,s[i:i+5])) for i in range(len(s)-4))

Then, to generalize it, as you can see, if you need max product of 4 numbers the first number is 5, so if you need max product of 13 numbers the first number should be 14, just pass two arguments to the function:

def greatest_product(s, n=13):
    return max(prod(map(int,s[i:i+n+1])) for i in range(len(s)-n))

Full code:

from math import prod
def greatest_product(s, n=13):
    return max(prod(map(int,s[i:i+n+1])) for i in range(len(s)-n))

• Place import names at top of script

I am sure you know if you copy paste your code into a console as is, it will raise NameErrors.

Put the following:

from functools import reduce
from itertools import islice
from math import prod

At the top of script.

Your second function is actually quite effictive, but not as effictive as it can be, you made a simple mistake, max can return the maximum value of more than two numbers, its arguments can be infinitely many or an iterable.

So it should be written as this:

def greatest_product(s):
    return max(prod(map(int,s[i:i+4])) for i in range(len(s)-4))

Then, to generalize it, as you can see, if you need max product of 4 numbers the first number is 4, so if you need max product of 13 numbers the first number should be 13, just pass two arguments to the function:

def greatest_product(s, n=13):
    return max(prod(map(int,s[i:i+n])) for i in range(len(s)-n))

Full code:

from math import prod
def greatest_product(s, n=13):
    return max(prod(map(int,s[i:i+n])) for i in range(len(s)-n))