py: Implement full behaviour of dict.update(), and dict().

Add keyword args to dict.update(), and ability to take a dictionary as
argument.

dict() class constructor can now use dict.update() directly.

This patch loses fast path for dict(other_dict), but is that really
needed?  Any anyway, this idiom will now re-hash the dictionary, so is
arguably more memory efficient.

Addresses issue #647.

py/objdict.c

@@ -40,7 +40,7 @@
 
 STATIC mp_obj_t mp_obj_new_dict_iterator(mp_obj_dict_t *dict, int cur);
 STATIC mp_map_elem_t *dict_it_iternext_elem(mp_obj_t self_in);
-STATIC mp_obj_t dict_copy(mp_obj_t self_in);
+STATIC mp_obj_t dict_update(uint n_args, const mp_obj_t *args, mp_map_t *kwargs);
 
 STATIC void dict_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
     mp_obj_dict_t *self = self_in;
@@ -61,40 +61,13 @@ STATIC void dict_print(void (*print)(void *env, const char *fmt, ...), void *env
 }
 
 STATIC mp_obj_t dict_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
-    mp_obj_t dict;
-    switch (n_args) {
-        case 0:
-            dict = mp_obj_new_dict(0);
-            break;
-
-        case 1: {
-            if (MP_OBJ_IS_TYPE(args[0], &mp_type_dict)) {
-                return dict_copy(args[0]);
-            }
-            // TODO create dict from an arbitrary mapping!
-
-            // Make dict from iterable of pairs
-            mp_obj_t iterable = mp_getiter(args[0]);
-            mp_obj_t dict = mp_obj_new_dict(0);
-            // TODO: support arbitrary seq as a pair
-            mp_obj_t item;
-            while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
-                mp_obj_t *sub_items;
-                mp_obj_get_array_fixed_n(item, 2, &sub_items);
-                mp_obj_dict_store(dict, sub_items[0], sub_items[1]);
-            }
-            return dict;
-        }
-
-        default:
-            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "dict takes at most 1 argument"));
-    }
-
-    // add to the new dict any keyword args
-    for (const mp_obj_t *a = args + n_args; n_kw > 0; n_kw--, a += 2) {
-        mp_obj_dict_store(dict, a[0], a[1]);
+    mp_obj_t dict = mp_obj_new_dict(0);
+    if (n_args > 0 || n_kw > 0) {
+        mp_obj_t args2[2] = {dict, args[0]}; // args[0] is always valid, even if it's not a positional arg
+        mp_map_t kwargs;
+        mp_map_init_fixed_table(&kwargs, n_kw, args + n_args);
+        dict_update(n_args + 1, args2, &kwargs); // dict_update will check that n_args + 1 == 1 or 2
     }
-
     return dict;
 }
 
@@ -348,31 +321,57 @@ STATIC mp_obj_t dict_popitem(mp_obj_t self_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(dict_popitem_obj, dict_popitem);
 
-STATIC mp_obj_t dict_update(mp_obj_t self_in, mp_obj_t iterable) {
-    assert(MP_OBJ_IS_TYPE(self_in, &mp_type_dict));
-    mp_obj_dict_t *self = self_in;
-    /* TODO: check for the "keys" method */
-    mp_obj_t iter = mp_getiter(iterable);
-    mp_obj_t next = NULL;
-    while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
-        mp_obj_t inneriter = mp_getiter(next);
-        mp_obj_t key = mp_iternext(inneriter);
-        mp_obj_t value = mp_iternext(inneriter);
-        mp_obj_t stop = mp_iternext(inneriter);
-        if (key == MP_OBJ_STOP_ITERATION
-            || value == MP_OBJ_STOP_ITERATION
-            || stop != MP_OBJ_STOP_ITERATION) {
-            nlr_raise(mp_obj_new_exception_msg(
-                         &mp_type_ValueError,
-                         "dictionary update sequence has the wrong length"));
+STATIC mp_obj_t dict_update(uint n_args, const mp_obj_t *args, mp_map_t *kwargs) {
+    assert(MP_OBJ_IS_TYPE(args[0], &mp_type_dict));
+    mp_obj_dict_t *self = args[0];
+
+    mp_arg_check_num(n_args, kwargs->used, 1, 2, true);
+
+    if (n_args == 2) {
+        // given a positional argument
+
+        if (MP_OBJ_IS_TYPE(args[1], &mp_type_dict)) {
+            // update from other dictionary (make sure other is not self)
+            if (args[1] != self) {
+                // TODO don't allocate heap object for this iterator
+                mp_obj_t *dict_iter = mp_obj_new_dict_iterator(args[1], 0);
+                mp_map_elem_t *elem = NULL;
+                while ((elem = dict_it_iternext_elem(dict_iter)) != MP_OBJ_STOP_ITERATION) {
+                    mp_map_lookup(&self->map, elem->key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = elem->value;
+                }
+            }
         } else {
-            mp_map_lookup(&self->map, key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;
+            // update from a generic iterable of pairs
+            mp_obj_t iter = mp_getiter(args[1]);
+            mp_obj_t next = NULL;
+            while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
+                mp_obj_t inneriter = mp_getiter(next);
+                mp_obj_t key = mp_iternext(inneriter);
+                mp_obj_t value = mp_iternext(inneriter);
+                mp_obj_t stop = mp_iternext(inneriter);
+                if (key == MP_OBJ_STOP_ITERATION
+                    || value == MP_OBJ_STOP_ITERATION
+                    || stop != MP_OBJ_STOP_ITERATION) {
+                    nlr_raise(mp_obj_new_exception_msg(
+                                 &mp_type_ValueError,
+                                 "dictionary update sequence has the wrong length"));
+                } else {
+                    mp_map_lookup(&self->map, key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;
+                }
+            }
+        }
+    }
+
+    // update the dict with any keyword args
+    for (machine_uint_t i = 0; i < kwargs->alloc; i++) {
+        if (MP_MAP_SLOT_IS_FILLED(kwargs, i)) {
+            mp_map_lookup(&self->map, kwargs->table[i].key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = kwargs->table[i].value;
         }
     }
 
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(dict_update_obj, dict_update);
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(dict_update_obj, 1, dict_update);
 
 
 /******************************************************************************/

tests/basics/dict_construct.py

+# dict constructor
+
+d = dict()
+print(d)
+
+d = dict({1:2})
+print(d)
+
+d = dict(a=1)
+print(d)
+
+d = dict({1:2}, a=3)
+print(d[1], d['a'])
+
+d = dict([(1, 2)], a=3, b=4)
+print(d[1], d['a'], d['b'])

tests/basics/dict_update.py

@@ -8,3 +8,9 @@ print(len(d))
 d.update([(1,4)])
 print(d[1])
 print(len(d))
+
+# using keywords
+d.update(a=5)
+print(d['a'])
+d.update([(1,5)], b=6)
+print(d[1], d['b'])