Get all of the possible products from a list of numbers

Question

The problem is indexing. I've tried this code snippet:

for i in range(2,len(the_list_im_getting_values_from)):
    for j in range(0,i+1):
        index[j] = j
    for k in range(0,len(index)):
        the_output_list.append(the_list_im_getting_values_from[index[k]]*the_list_im_getting_values_from[index[k+1]])
        k += 1

, but it totally didn't work.

How to solve this problem?

Example input: array of 3, 4 and 7

Example output: [12,21,28,84]

Processing stages:

3*4=12 
3*7=21 
4*7=28 
3*4*7=84 

[12,21,28,84]

Answer 1

You can play around with itertools multiset-receipt . It will generate somewhat more of the needed tuples, you would have to filter them out:

from itertools import chain, combinations

# see link above for credits
def powerset(iterable):
    "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))

def mult(iterab):
    """Multiply all numbers in the iterable and return result"""
    rv = 1
    for k in iterab:
        rv = rv * k
    return rv


d = [3,4,7]
k = powerset(d) # (), (3,), (4,), (7,), (3, 4), (3, 7), (4, 7), (3, 4, 7)

result = []

# we filter out anything from k thats shorter then 2
result.extend(map(mult, (x for x in k if len(x)>1))) 

print(result)

Output:

[12, 21, 28, 84]

Answer 2

So you're trying to get all products using every possible combination of numbers in your list.

from itertools import chain, combinations
from functools import reduce

def powerset(iterable, min_subset_size=1):
    'Returns all subsets of the iterable larger than the given size.'
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(min_subset_size, len(s)+1))

def product(iterable):
    'Returns the product of all the numbers in the iterable.'
    return reduce((lambda x, y: x * y), iterable)

numbers =  3, 4, 7

If eg 3 counts as a product of a single number:

result = {product(subset) for subset in powerset(numbers)}
print(result)
Out: {3, 4, 7, 12, 84, 21, 28}

If a product must be of 2 or more numbers eg 3*4, 3*4*7:

result = {product(subset) for subset in powerset(numbers, 2)}
print(result)
Out: {28, 12, 21, 84}

Answer 3

I think what you want is the result of each number multiplied by the other ints in the list? Thus for list[3,4,7] you would want 9,16,49,12,21,28. You can try this.

l = [3,4,7]
s = set()
for count, num in enumerate(l):
    for each in l:
        s.add(each * l[count])

s
{9, 12, 16, 49, 21, 28}

if you dont want the squares (9,49,16) add

if list[count] == each:
    countinue

underneath the second for loop