X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FCensus.py;h=b72da0cbd7133e66f9fb9f5c63b7c641fc58180a;hb=HEAD;hp=63f69aaccaadf355b7d1b82414841e1d2839111b;hpb=0139658183fcfe4d53b7f6c2051955c8da5d05d1;p=dead%2Fcensus-tools.git

diff --git a/src/Census.py b/src/Census.py
index 63f69aa..b72da0c 100644
--- a/src/Census.py
+++ b/src/Census.py
@@ -25,7 +25,10 @@ class Database:
 
 
     def __del__(self):
-        self.connection.close()
+        try:
+            self.connection.close()
+        except:
+            pass
 
 
     def find_average_population_density(self, coords):
@@ -36,9 +39,8 @@ class Database:
                 
         query = """
         SELECT population_density
-        FROM (sf1_blocks INNER JOIN tiger_blocks
-              ON sf1_blocks.blkidfp00=tiger_blocks.blkidfp00)
-        WHERE ST_Contains(tiger_blocks.the_geom,
+        FROM blocks
+        WHERE ST_Contains(blocks.the_geom,
                           ST_SetSRID(ST_Point(%.6f, %.6f), %d));
         """
         
@@ -46,11 +48,12 @@ class Database:
         cursor.execute(query, sql_params)        
         rows = cursor.fetchall()
         cursor.close()
-        
-        if len(rows) > 0:
+
+        # SQL queries that return no results get returned as [[None]].
+        if rows[0][0] != None:
             return rows[0][0]
         else:
-            return None
+            return 0
 
 
     def find_contained_population(self, well_known_text):
@@ -60,7 +63,7 @@ class Database:
         """
         cursor = self.connection.cursor()
 
-        # We're ready to build our query, one step at a time. Firsy, we store
+        # We're ready to build our query, one step at a time. First, we store
         # the Text->Geom conversion in a variable; this just makes the query a
         # little easier to read.
         geometric_object = "ST_GeomFromText(%s, %d)"
@@ -76,9 +79,9 @@ class Database:
         # result.
         #
         query = """
-        SELECT SUM(sf1_blocks.pop100 *
-                   ( ST_Area(ST_Intersection(%s, tiger_blocks.the_geom))
-                   / ST_Area(tiger_blocks.the_geom) )
+        SELECT SUM(pop100 *
+                   ( ST_Area(ST_Intersection(%s, blocks.the_geom))
+                   / ST_Area(blocks.the_geom) )
                ) AS covered_population
                """ % geometric_object
         sql_params = (well_known_text, self.srid)
@@ -87,15 +90,14 @@ class Database:
         # Join our two block tables, so that we have both the demographic
         # and geometric data.
         query += """
-        FROM (sf1_blocks INNER JOIN tiger_blocks
-              ON sf1_blocks.blkidfp00 = tiger_blocks.blkidfp00)
+        FROM blocks
         """
 
 
         # We only need to calculate the covered population for the blocks
         # that actually intersect our object.
         query += """
-        WHERE (ST_Intersects(%s, tiger_blocks.the_geom))
+        WHERE (ST_Intersects(%s, blocks.the_geom))
         """ % geometric_object
         # geometric_object hasn't been substituted yet, so we need
         # to add the sql_params twice.
@@ -112,10 +114,11 @@ class Database:
         rows = cursor.fetchall()
         cursor.close()
 
-        if (len(rows) > 0):
+        # SQL queries that return no results get returned as [[None]].
+        if rows[0][0] != None:
             return rows[0][0]
         else:
-            return None
+            return 0
 
 
 
@@ -127,9 +130,9 @@ class Database:
         cursor = self.connection.cursor()
 
         query = """
-        SELECT ST_AsText(tiger_blocks.the_geom)
-        FROM tiger_blocks
-        WHERE tiger_blocks.blkidfp00 = %s;
+        SELECT ST_AsText(the_geom)
+        FROM blocks
+        WHERE blkidfp00 = %s;
         """
         sql_params = (blkidfp00,)
 
@@ -137,8 +140,7 @@ class Database:
         rows = cursor.fetchall()
         cursor.close()
 
-        if len(rows) > 0:
-            return rows[0][0]
-        else:
-            return None
+        # Just pass on the None if that's what we got from the
+        # database.
+        return rows[0][0]