Merge from trunk

[plcapi.git] / trunk / psycopg2 / examples / cursor.py

diff --git a/trunk/psycopg2/examples/cursor.py b/trunk/psycopg2/examples/cursor.py
new file mode 100644 (file)
index 0000000..54cb5e7
--- /dev/null
+++ b/trunk/psycopg2/examples/cursor.py
@@ -0,0 +1,63 @@
+# cursor.py - how to subclass the cursor type
+#
+# Copyright (C) 2004 Federico Di Gregorio  <fog@debian.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+# for more details.
+
+## put in DSN your DSN string
+
+DSN = 'dbname=test'
+
+## don't modify anything below this line (except for experimenting)
+
+import sys
+import psycopg2
+import psycopg2.extensions
+
+if len(sys.argv) > 1:
+    DSN = sys.argv[1]
+
+print "Opening connection using dsn:", DSN
+conn = psycopg2.connect(DSN)
+print "Encoding for this connection is", conn.encoding
+
+
+class NoDataError(psycopg2.ProgrammingError):
+    """Exception that will be raised by our cursor."""
+    pass
+
+class Cursor(psycopg2.extensions.cursor):
+    """A custom cursor."""
+
+    def fetchone(self):
+        """Like fetchone but raise an exception if no data is available.
+
+        Note that to have .fetchmany() and .fetchall() to raise the same
+        exception we'll have to override them too; even if internally psycopg
+        uses the same function to fetch rows, the code path from Python is
+        different.
+        """
+        d = psycopg2.extensions.cursor.fetchone(self)
+        if d is None:
+           raise NoDataError("no more data")
+        return d
+    
+curs = conn.cursor(cursor_factory=Cursor)
+curs.execute("SELECT 1 AS foo")
+print "Result of fetchone():", curs.fetchone()
+
+# now let's raise the exception
+try:
+    curs.fetchone()
+except NoDataError, err:
+    print "Exception caugth:", err  
+
+conn.rollback()