arr = [1, 2, 3, 2, 4, 5, 1, 3] ''' def repeating_numbers(inp): count = {} result = [] for i in inp: count[i] = count.get(i,0)+1 for i in count: if count[i] >= 2: result.append(i) return result print(repeating_numbers(arr)) ''' def repeating_numbers(inp): seen = set() duplicates = set() for i in inp: if i in seen: duplicates.add(i) else: seen.add(i) return list(duplicates) print(repeating_numbers(arr))