Implement str.rpartition and add tests for it.

py/objstr.c

@@ -545,6 +545,40 @@ STATIC mp_obj_t str_partition(mp_obj_t self_in, mp_obj_t arg) {
     return mp_obj_new_tuple(3, items);
 }
 
+STATIC mp_obj_t str_rpartition(mp_obj_t self_in, mp_obj_t arg) {
+    assert(MP_OBJ_IS_STR(self_in));
+    if (!MP_OBJ_IS_STR(arg)) {
+        nlr_jump(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
+                                               "Can't convert '%s' object to str implicitly", mp_obj_get_type_str(arg)));
+    }
+
+    GET_STR_DATA_LEN(self_in, str, str_len);
+    GET_STR_DATA_LEN(arg, sep, sep_len);
+
+    if (sep_len == 0) {
+        nlr_jump(mp_obj_new_exception_msg(&mp_type_ValueError, "empty separator"));
+    }
+
+    if (sep_len > str_len) {
+        goto not_found;
+    }
+
+    for (machine_uint_t str_index = str_len; ; str_index--) {
+        if (memcmp(&str[str_index - sep_len], sep, sep_len) == 0) {
+            mp_obj_t items[] = {mp_obj_new_str(str, str_index - sep_len, false), arg,
+                                mp_obj_new_str(str + str_index, str_len - str_index, false)};
+            return mp_obj_new_tuple(3, items);
+        }
+        if (str_index - sep_len == 0) {
+            break;
+        }
+    }
+
+not_found: ;
+    mp_obj_t items[] = {MP_OBJ_NEW_QSTR(MP_QSTR_), MP_OBJ_NEW_QSTR(MP_QSTR_), mp_obj_new_str(str, str_len, false)};
+    return mp_obj_new_tuple(3, items);
+}
+
 STATIC machine_int_t str_get_buffer(mp_obj_t self_in, buffer_info_t *bufinfo, int flags) {
     if (flags == BUFFER_READ) {
         GET_STR_DATA_LEN(self_in, str_data, str_len);
@@ -568,6 +602,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR(str_format_obj, 1, str_format);
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_replace_obj, 3, 4, str_replace);
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_count_obj, 2, 4, str_count);
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(str_partition_obj, str_partition);
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(str_rpartition_obj, str_rpartition);
 
 STATIC const mp_method_t str_type_methods[] = {
     { "find", &str_find_obj },
@@ -579,6 +614,7 @@ STATIC const mp_method_t str_type_methods[] = {
     { "replace", &str_replace_obj },
     { "count", &str_count_obj },
     { "partition", &str_partition_obj },
+    { "rpartition", &str_rpartition_obj },
     { NULL, NULL }, // end-of-list sentinel
 };
 

tests/basics/string_rpartition.py

+print("asdf".rpartition('g'))
+print("asdf".rpartition('a'))
+print("asdf".rpartition('s'))
+print("asdf".rpartition('f'))
+print("asdf".rpartition('d'))
+print("asdf".rpartition('asd'))
+print("asdf".rpartition('sdf'))
+print("asdf".rpartition('as'))
+print("asdf".rpartition('df'))
+print("asdf".rpartition('asdf'))
+print("asdf".rpartition('asdfa'))
+print("asdf".rpartition('fasdf'))
+print("asdf".rpartition('fasdfa'))
+print("abba".rpartition('a'))
+print("abba".rpartition('b'))
+
+try:
+    print("asdf".rpartition(1))
+except TypeError:
+    print("Raised TypeError")
+else:
+    print("Did not raise TypeError")
+
+try:
+    print("asdf".rpartition(''))
+except ValueError:
+    print("Raised ValueError")
+else:
+    print("Did not raise ValueError")