Create an external object in Python:

The keys displayed for functions in Python differ between a built-in function and a user-defined function:

Define an object in Python and display it:

Delete the session:

ExternalOperation can be used to extract the operation from an ExternalObject:

The same can be done with an ExternalFunction:

ExternalOperation can be used as an argument to ExternalObject:

The executed operation is identical to the following one:

Which can be executed with ExternalEvaluate:

The result is equivalent to running the following Python code:

Create an ExternalObject to work with the sys module:

When a string is used, the "GetAttribute" operation is executed in most evaluators, including Python:

The result is equivalent to running an explicit "GetAttribute" operation:

Start a Python session:

Create an ExternalObject:

Use ExternalFunction to run methods on the object:

Close the session:

Start a Python session:

Create an ExternalObject for the datetime module:

Create an ExternalObject with the current date and another one with a timedelta:

Send back the objects using an ExternalFunction:

The same can be done with an ExternalEvaluate call:

Use "ReturnType" to return a String:

Close the session:

Multiple operations can be concatenated using multiple arguments in ExternalObject:

Which can be written in a more compact way:

Running successive operations using downvalues can lead to undefined behavior without checking the return value at every step:

This is happening because the first operation is returning an ExternalFunction (since date is a class that can be initialized) and you are passing an incomplete ExternalOperation to the date constructor:

In order to safely chain operations without checking the return type at every step, run all operations at once:

A Failure object is returned as soon as any operation fails, preventing others from running:

Delete the session:

Start a Python session to play chess:

Create an ExternalObject to represent that state of the chess board:

Define a function to plot the board:

Use the function to plot the board:

Extract the current move number by extracting an attribute from the object:

Move a piece by running a function; it will change the state of the external object:

Plot the board again to display the new configuration:

You can now compute all legal moves that can be done with the current configuration:

Create a method caller for the "UCI" property by chaining external operations:

Compute the UCI string for one move:

You can now execute one random move:

You can use the plot function to show the board again:

Create a function to play random moves:

Play some random chess:

Show the current move counter:

Delete the session: