Generate combinations without using itertools

Question

I need to fix/modify this code I have here so that the output will be like this:

This is the code:

num_list = [1, 2, 3]
def combination_generator(num_list):
    pool = tuple(num_list)
    n = len(pool)
    if range(num_list) > n:
        return
        indices = list(range(num_list))
        yield tuple(pool[i] for i in indices)
        while True:
            for i in reversed(range(num_list)):
                if indices[i] != i + n - range(num_list):
                    break
    else:
        return
        indices[i] += 1
        for j in range(i+1, range(num_list)):
            indices[j] = indices[j-1] + 1
        yield tuple(pool[i] for i in indices)

print(combination_generator(num_list))

Note: I am not allowed to use any imports. so I can't use itertools. Also, it must also function with a higher number of values if added in the list.

Any help?

Answer 1

num_list = [1, 2, 3]

def combination_generator(attrs):

    attrs = list(attrs)

    if len(attrs) <= 1:
        yield attrs
        yield []
    else:
        for item in combination_generator(attrs[1:]):
            yield [attrs[0]]+item
            yield item

print(combination_generator(num_list))
print([i for i in combination_generator(num_list)])
print([set(i) for i in combination_generator(num_list)]) # if you nead a list[set]

output:

<generator object powerset at 0x0000022B7E8046D0>     
[[1, 2, 3], [2, 3], [1, 3], [3], [1, 2], [2], [1], []]
[{1, 2, 3}, {2, 3}, {1, 3}, {3}, {1, 2}, {2}, {1}, {}]