Implement City.each_within_poly()

lib/xmet/city.py

@@ -1,6 +1,7 @@
 import csv
 import shapely
 
+from xmet.db    import Database
 from xmet.coord import COORD_SYSTEM
 
 """
@@ -61,3 +62,22 @@ class City():
                     row[i] = row[i].rstrip()
 
                 yield City.from_tsv_row(row)
+
+    @staticmethod
+    def each_within_poly(db: Database, poly: shapely.Polygon):
+        sql = """
+            select
+                *
+            from
+                xmet_city
+            where
+                ST_Within(location, GeomFromText(:poly, 4326)) = 1
+            order by
+                population desc
+        """
+
+        st = db.query_sql(City, sql, {
+            'poly': shapely.to_wkt(poly)
+        })
+
+        yield from st.each()