How to set the font's size of the GtkLabel?

["Lazy Fox" <lazy fox wu gmail com>]

I wrote the following statememts to set a GtkLabel's font size.
But it seems don't work?
I'm not good at Pango, can anybody help me?
+-------------------------------------------------------------------------------------------
| PangoAttrList *pg_attr_list = pango_attr_list_new();
| PangoAttribute *pg_attr = pango_attr_size_new(10);
|
| label = gtk_label_new("This is a label");
| pango_attr_list_change(pg_attr_list, pg_attr);
| gtk_label_set_attributes(GTK_LABEL(label), pg_attr_list);
+------------------------------------------------------------------------------------------