Python Interface

The simplest way to invoke custom Python code from a toplevel VentureScript program are the pyexec and pyeval inference actions (which see).

For more elaborate integrations, one can write a plugin. In a plugin, one can

• Define callbacks
• Define foreign stochastic procedures for the inference language
• Define foreign stochastic procedures for the modeling language
• Manipulate Venture programmatically for any other purpose also

Plugins and Callbacks

A Venture plugin is just a Python module that defines a toplevel function called __venture_start__.

• To load a plugin when invoking Venture from the command line, pass -L <filename>.
• To load a plugin when using Venture as a Python library, call ripl.load_plugin(filename).
• To load a plugin from a VentureScript inference program, use the load_plugin action (which see).

Any of these will load the plugin in the given file, and call its __venture_start__ function with one argument, namely the Ripl object representing the current Venture session. The plugin is then free to invoke what methods it will on that Ripl.

If extra arguments are passed to either the ripl method load_plugin or the inference action load_plugin, those will be forwarded to the plugin’s __venture_start__ function. If __venture_start__ returns a value, that value will be returned by load_plugin. There is currently no way to pass arguments to a plugin loaded from the command line, nor to capture any value that it might return.

Useful ripl methods to call from a plugin’s __venture_start__:

• bind_callback(name, callable) to bind a given Python function as a call back that can be invoked with call_back (which see)
• bind_foreign_sp(name, SP) to bind a foreign stochastic procedure for the model language TODO: Document the stochastic procedure interface in this reference manual
• bind_foreign_inference_sp(name, SP) to bind a foreign stochastic procedure for the inference language TODO: Document the stochastic inference procedure interface in this reference manual

Built-in Callbacks

• Callback timer_time

  Print the time that has elapsed since the timer was started by timer_start.

• Callback timer_resume

  Resume a timer paused by timer_pause.

• Callback timer_start

  Start a timer.

  Resets any currently running timer that was started using timer_start.

• Callback timer_pause

  Pause the timer started by timer_start.

  This is mainly for cumulative measurements (e.g. benchmarking) where some sections should be excluded.