default_db = None
user = None

# default_db = [1, 2, 3]
# user = [4, 5, 6]
default = [1, 4, 8, 9, 10]



if default_db or user:
    default_db = [] if default_db is None
    user = [] if user is None
    full = default_db + user
else:
    full = default
print(full)