Mitchell McMullenPaul Nguyen

SWAN

• Python written entirely in C#.• Can access all .NET libraries and

Silverlight.• Created by the same guy as Jython.• No design documentation or developer’s

guide for source code =(

IronPySwan• Added Oracle Database Connectivity.• Embedded SQL commands/queries.• Allows arbitrary python expressions within

SQL commands/queries. (Using back ticks)

Overview

Tokenizer• Breaks up the source code into tokens.• IronPython uses a mostly hand-written

tokenizer and parser.• Some token recognition code is auto-

generated.

MAKECONNECT

INSERT

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Parser• Identifies tokens as they come in.• Implements the Python (BNF) grammar directly.• Constructs the Python AST.

MSAstNode Declaration• This is where a statement/expression is turned

into a node fit for the AST.• The statement/expression’s Reduce() method is

called, which returns a simpler node. • Typically, reduce() links to implementation code.

AstMethods• Big collection of Method signatures, used

for reflection/indirection to PythonOps.

ConnectionStatement (Nonquery)Expression (Query)

AstMethods

PythonOps• Pretty much another layer of indirection,

and a repository for some helper functions.

ConnectionStatement (Nonquery)Expression (Query)

Runtime Behavior• This is the implementation-ey kind of stuff. In the

end, this is where the heavy lifting for each method call is located.

• We have one class, PySwanSqlRunner, which houses the connection and passes the final SQL strings on to the database.

• These methods are executed by the interpreter.

PySwanSqlRunnerConnectionStatement (Nonquery)Expression (Query)

Stuff That Still Really Needs Work

• Error handling is pretty primitive.• No RDF. (Sorry, Dr. Cannata!!)• SQL must be well-formed.

Programming Language Terms• Terminal/Nonterminal (Tokenizer.cs).• Abstract Syntax Tree (Parser.cs).• Parse tree is implicitly built.

(Parser.cs)• Python.g BNF is implemented directly

(Parser.cs• Some SQL involved.

Demonstration• Hope you enjoy!

Questions?