objstr: Add note that replace() is nicely optimized.

Doesn't allocate memory and returns original string if no replacements are
to be made.

1 files changed, 2 insertions, 0 deletions

diff --git a/py/objstr.c b/py/objstr.c
index d11f097fca..0afc538b01 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -1465,6 +1465,8 @@ not_enough_args:
     return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
 }
 
+// The implementation is optimized, returning the original string if there's
+// nothing to replace.
 STATIC mp_obj_t str_replace(mp_uint_t n_args, const mp_obj_t *args) {
     assert(MP_OBJ_IS_STR_OR_BYTES(args[0]));