In 3.6 typing types are pickled by names: >>> import pickle, pickletools, typing >>> pickletools.optimize(pickle.dumps(typing.List)) b'\x80\x03ctyping\nList\n.' >>> pickletools.dis(pickletools.optimize(pickle.dumps(typing.List))) 0: \x80 PROTO 3 2: c GLOBAL 'typing List' 15: . STOP highest protocol among opcodes = 2 The side effect of this is that they are considered atomic by the copy module. In 3.7 the pickle data contains all private attributes. >>> pickletools.optimize(pickle.dumps(typing.List)) b'\x80\x03ctyping\n_GenericAlias\n)\x81}(X\x05\x00\x00\x00_inst\x89X\x08\x00\x00\x00_special\x88X\x05\x00\x00\x00_nameX\x04\x00\x00\x00ListX\n\x00\x00\x00__origin__cbuiltins\nlist\nX\x08\x00\x00\x00__args__ctyping\nTypeVar\n)\x81q\x00}(X\x04\x00\x00\x00nameX\x01\x00\x00\x00TX\x05\x00\x00\x00boundNX\x0b\x00\x00\x00constraints)X\x02\x00\x00\x00co\x89X\x06\x00\x00\x00contra\x89ub\x85X\x0e\x00\x00\x00__parameters__h\x00\x85X\t\x00\x00\x00__slots__Nub.' >>> pickletools.dis(pickletools.optimize(pickle.dumps(typing.List))) 0: \x80 PROTO 3 2: c GLOBAL 'typing _GenericAlias' 24: ) EMPTY_TUPLE 25: \x81 NEWOBJ 26: } EMPTY_DICT 27: ( MARK 28: X BINUNICODE '_inst' 38: \x89 NEWFALSE 39: X BINUNICODE '_special' 52: \x88 NEWTRUE 53: X BINUNICODE '_name' 63: X BINUNICODE 'List' 72: X BINUNICODE '__origin__' 87: c GLOBAL 'builtins list' 102: X BINUNICODE '__args__' 115: c GLOBAL 'typing TypeVar' 131: ) EMPTY_TUPLE 132: \x81 NEWOBJ 133: q BINPUT 0 135: } EMPTY_DICT 136: ( MARK 137: X BINUNICODE 'name' 146: X BINUNICODE 'T' 152: X BINUNICODE 'bound' 162: N NONE 163: X BINUNICODE 'constraints' 179: ) EMPTY_TUPLE 180: X BINUNICODE 'co' 187: \x89 NEWFALSE 188: X BINUNICODE 'contra' 199: \x89 NEWFALSE 200: u SETITEMS (MARK at 136) 201: b BUILD 202: \x85 TUPLE1 203: X BINUNICODE '__parameters__' 222: h BINGET 0 224: \x85 TUPLE1 225: X BINUNICODE '__slots__' 239: N NONE 240: u SETITEMS (MARK at 27) 241: b BUILD 242: . STOP highest protocol among opcodes = 2 Unpickling it creates a new object. And I'm not sure all invariants are satisfied. In additional to lesses efficiency and lost of preserving identity, such pickle can be incompatible with old Python versions and future Python versions if the internal representation of typing types will be changed.