Nested Program Blocks (Python)

From within Python, you can submit command syntax containing a BEGIN PROGRAM block, thus allowing you to nest program blocks. This can be done by including the nested program block in a separate command syntax file and submitting an INSERT command to read in the block. It can also be done by submitting the nested program block from within a user-defined Python function.

Example: Nesting program blocks using the INSERT command

import spss
spss.Submit("INSERT FILE='/myprograms/nested_block.sps'.")

The file /myprograms/nested_block.sps would contain a BEGIN PROGRAM block, as in:

BEGIN PROGRAM PYTHON3.
import spss
<Python code>
END PROGRAM.
Note: You cannot import a Python module containing code that nests a program block, such as the above code that uses the INSERT command to insert a file containing a program block. If you wish to encapsulate nested program blocks in a Python module that can be imported, then embed the nesting code in a user-defined function as shown in the following example.

Example: Nesting program blocks with a user-defined Python function

import spss, myfuncs
myfuncs.demo()
  • myfuncs is a user-defined Python module containing the function (demo) that will submit the nested program block.

    A Python module is simply a text file containing Python definitions and statements. You can create a module with a Python IDE, or with any text editor, by saving a file with an extension of .py. The name of the file, without the .py extension, is then the name of the module.

  • The import statement includes myfuncs so that it is loaded along with the spss module. To be sure that Python can find your module, you may want to save it to your Python "site-packages" directory, typically /Python310/Lib/site-packages.
  • The code myfuncs.demo() calls the function demo in the myfuncs module.

Following is a sample of the contents of myfuncs. 

import spss
def demo():
   spss.Submit("""
BEGIN PROGRAM PYTHON3.
<Python code>
END PROGRAM.""")
  • The sample myfuncs module includes an import spss statement. This is necessary since a function in the module makes use of a function from the spss module--specifically, the Submit function.
  • The nested program block is contained within a Python triple-quoted string. Triple-quoted strings allow you to specify a block of commands on multiple lines, resembling the way you might normally write command syntax.
  • Notice that spss.Submit is indented but the BEGIN PROGRAM block is not. Python statements that form the body of a user-defined Python function must be indented. The level of indentation is arbitrary but must be the same for all statements in the function body. The BEGIN PROGRAM block is passed as a string argument to the Submit function and is processed by IBM® SPSS® Statistics as a block of Python statements. Python statements are not indented unless they are part of a group of statements, as in a function or class definition, a conditional expression, or a looping structure.

Notes

  • You can have up to five levels of nesting.
  • Python variables specified in a nested program block are local to that block unless they are specified as global variables. In addition, Python variables specified in a program block that invokes a nested block can be read, but not modified, in the nested block.
  • Nested program blocks can be Python program blocks or R program blocks.
  • If a Submit function containing a triple quoted string nests a Python program block containing another triple quoted string, use a different type of triple quotes in the nested block. For example, if the outer block uses triple double quotes, then use triple single quotes in the nested block.