Combination_Sum.py

def combinations(data, length):
    def dfs(cur, pos):
        if len(cur) == length:
            yield cur
        if pos == len(data):
            return
        if type(data) is list:
            for i in range(pos, len(data)):
                for j in dfs(cur + [data[i]], i + 1):
                    yield j
        else:
            for i in range(pos, len(data)):
                for j in dfs(cur + data[i], i + 1):
                    yield j
    if type(data) is list:        
        return dfs([], 0)
    else:        
        return dfs("", 0)

'''
for i in combinations([1, 2, 3, 4], 2):
    print(i)
for i in combinations(['a', 'b', 'c', 'd'], 2):
    print(i)
for i in combinations('abcd', 2):
    print(i)
'''

ans = []
target = 7
for j in range(1,len([2, 2, 2, 3, 3, 6, 7])):
    for i in combinations([2, 2, 2, 3, 3, 6, 7], j):
        #print(i)
        if sum(i) == target:
            #print(i)
            if i not in ans:
                ans.append(i)
print(ans)