from functools import reduce
import operator
d = [[1],[2],[3],[3]]
flattened_list = sum(d, [])
print(flattened_list)
flattened_list = reduce(operator.concat, d)
print(flattened_list)
ZnJvbSBmdW5jdG9vbHMgaW1wb3J0IHJlZHVjZQppbXBvcnQgb3BlcmF0b3IKCmQgPSBbWzFdLFsyXSxbM10sWzNdXQpmbGF0dGVuZWRfbGlzdCA9IHN1bShkLCBbXSkKcHJpbnQoZmxhdHRlbmVkX2xpc3QpCgpmbGF0dGVuZWRfbGlzdCA9IHJlZHVjZShvcGVyYXRvci5jb25jYXQsIGQpCnByaW50KGZsYXR0ZW5lZF9saXN0KQ==