Adding commas to my integer

I have a very large integer value such as 2874. I wrote a function that can return me a list containing all possible outcomes if I start placing commas between this large integer value. How can i reduce the complexity of this function

Input:

2874

Output:

[[2874],[2,874],[28,74],[287,4],[2,8,74],[2,87,4],[28,7,4],[2,8,7,4]]

Explanation:

#zero commas
[2874]
#one comma
[2,874]
[28,74]
[287,4]
#two commas
[2,8,74]
[2,87,4]
[28,7,4]
#three commas
[2,8,7,4]

This is my code:

a=2874
def splitter(a):
    empty_list = []
    temp = str(a)
    if len(temp) ==1:
        return [[temp]]
    else:
        j=1
        for i in range(len(temp)-1):
            res = [temp[:j], temp[j:]]
            empty_list.append(res)
            j+=1
        return empty_list
def add_commas(a):
    final_list = [[str(a)]]
    for i in splitter(a):
        final_list.append(i)
    level=1
    n = 0
    for z in range(2):
        for m in range(len(final_list) - 1):
            m+=n
            temp = final_list[m + 1]
            unchanged = temp[:level]
            changed = temp[level:]
            if len(changed)>0 and len(temp)!= len(str(a)):
                after_part = splitter(changed[0])
                for i in after_part:
                    res = unchanged + i
                    final_list.append(res)
        n += 3
        level += 1
    unique_list = []
    for x in final_list:
        x = [int(i) for i in x]
        if x not in unique_list:
            unique_list.append(x)
    return unique_list

print(add_commas(a))