1 files changed, 64 insertions, 0 deletions
diff --git a/examples/cursor.py b/examples/cursor.py
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+++ b/examples/cursor.py
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+# 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 psycopg
+import psycopg.extensions
+
+if len(sys.argv) > 1:
+    DSN = sys.argv[1]
+
+print "Opening connection using dsn:", DSN
+
+conn = psycopg.connect(DSN)
+print "Encoding for this connection is", conn.encoding
+
+
+class NoDataError(psycopg.ProgrammingError):
+    """Exception that will be raised by our cursor."""
+    pass
+
+class Cursor(psycopg.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 = psycopg.extensions.cursor.fetchone(self)
+        if d is None:
+	    raise NoDataError("no more data")
+        return d
+    
+curs = conn.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()