Added the Census module.

[dead/census-tools.git] / src / Census.py

diff --git a/src/Census.py b/src/Census.py
new file mode 100644 (file)
index 0000000..eff25d4
--- /dev/null
+++ b/src/Census.py
@@ -0,0 +1,46 @@
+import pgdb
+
+import GPS
+
+
+class Database:
+    """
+    This class wraps all of the operations that we'd like to perform
+    on the census database. Most of the utility scripts will just call
+    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 __del__(self):
+        self.connection.close()
+
+        
+    def find_average_population_density(self, coords):
+        """
+        Find the average population density at a set of GPS coordinates.
+        """
+        cursor = self.connection.cursor()
+                
+        query = """
+        SELECT population_density
+        FROM (sf1_blocks INNER JOIN tiger
+              ON sf1_blocks.tiger_blkidfp00=tiger.blkidfp00)
+        WHERE ST_Contains(tiger.the_geom,
+                          ST_SetSRID(ST_Point(%.6f, %.6f), %d));
+        """
+        
+        sql_params = (coords.longitude, coords.latitude, self.srid)        
+        cursor.execute(query, sql_params)        
+        rows = cursor.fetchall()
+        
+        if len(rows) > 0:
+            return rows[0][0]
+        else:
+            return None
+