For most systems, the default return type is "Expression":

Numbers, strings, lists and associations are automatically imported for the "Expression" return type:

The return type of "String" returns a string of the result in the external language:

When using a database, the default return type is "Dataset":

"ReturnType" can be used to return data in a different form:

Evaluate code using a specified "Evaluator":

When using a File with the "SQL" evaluator, the evaluator can be a path to an SQLite file or a DatabaseReference specification:

An Association can be used to evaluate code in a Python provisioned environment:

Register an evaluator using a name:

Use the registered evaluator by referring to it by name:

Use "SessionProlog" to perform a side effect at the start of a session:

Start an external session and import a library at the beginning of the session:

Evaluate a function from the imported library:

Delete the session object:

Use "SessionEpilog" to perform a side effect at the end of a session:

Use "Prolog" to perform a side effect before every evaluation:

Use "Epilog" to perform a side effect after every evaluation:

When a string is provided, the command is directly executed:

The above is equivalent to writing the command using this form:

Use a File wrapper to run the code from a file:

The above is equivalent to writing the command using this form:

Use a URL wrapper to directly run code hosted online:

The above is equivalent to writing the command using this form:

Put code in a CloudObject:

Evaluate directly from the cloud:

The above is equivalent to writing the command using this form:

ExternalOperation can be used in "Command":

If needed, arguments can be used to call the operation:

ExternalFunction can be used in "Command":

Start a Python session:

Create an ExternalObject:

Call the object using "Command" and "Arguments":

When using only "Command", the object will be casted to the default "ReturnType":

Delete the object:

Specifying a "ReturnType" in the command overrides the "ReturnType" for the session:

Use "Arguments" to call the command with arguments:

For a single argument, you do not need to use a list:

If you need to pass a list as first argument, you need to wrap it with an extra list explicitly:

You can define a function inside "Command" and directly call it with "Arguments":

The same result can be achieved by using a Rule:

An alternative method is to define an ExternalFunction:

ExternalOperation can be used in "Arguments":

Start a Python session:

Create an ExternalObject:

Use the object in a function call:

Delete the object:

Use "Constants" to permanently set global variables before the command runs:

ExternalOperation can be used in "Constants":

ExternalFunction can be used in "Constants":

When running a command, you can inline a TemplateExpression:

You can explicitly fill TemplateSlot using "TemplateArguments":

If you need to pass a list as first argument, you need to wrap it with an extra list explicitly:

You can name template slots and use an Association to pass named arguments to the template:

ExternalOperation can be used in "TemplateArguments":

ExternalFunction can be used in "TemplateArguments":