X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FCensus.py;h=1b203124916535ae424cc35a1a714dea4de34d27;hb=77929a35679206577cfaeb2d64936b05d3d6ab5b;hp=da9283d2efb20c4c7d1f8896b120fad8f98b3815;hpb=0e8428f00f565a3e1791e19098ab59442972fa09;p=dead%2Fcensus-tools.git

diff --git a/src/Census.py b/src/Census.py
index da9283d..1b20312 100644
--- a/src/Census.py
+++ b/src/Census.py
@@ -1,5 +1,6 @@
 import pgdb
 
+import Configuration.Defaults
 import GPS
 import SummaryFile1
 
@@ -11,11 +12,16 @@ class Database:
     one or two methods from within this class.
     """
 
-    def __init__(self, _host, _database, _username, _srid):
-        self.connection = pgdb.connect(host=_host,
-                                       database=_database,
-                                       user=_username)
-        self.srid = _srid
+    def __init__(self,
+                 initial_host=Configuration.Defaults.DATABASE_HOST,
+                 initial_database=Configuration.Defaults.DATABASE_NAME,
+                 initial_username=Configuration.Defaults.DATABASE_USERNAME,
+                 initial_srid=Configuration.Defaults.SRID):
+        
+        self.connection = pgdb.connect(host=initial_host,
+                                       database=initial_database,
+                                       user=initial_username)
+        self.srid = initial_srid
 
 
     def __del__(self):
@@ -30,9 +36,8 @@ 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));
         """
         
@@ -40,11 +45,12 @@ 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):
@@ -54,7 +60,7 @@ 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)"
@@ -70,9 +76,9 @@ 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)
@@ -81,15 +87,14 @@ 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.
@@ -106,10 +111,11 @@ 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
 
 
 
@@ -121,9 +127,9 @@ 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,)
 
@@ -131,8 +137,7 @@ 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]