Python Topology API

• Streams Version 4.2 (or later).
• Python 3.5, 3.6, or 3.7
  • Either install Anaconda or Miniconda - this are the easiest options. When running distributed the Streams instance application environment variable PYTHONHOME must be set to the install location.
  • or install CPython. This is more involved and usually requires building Python from source code.

import mymodule
from streamsx.topology.topology import *
import streamsx.topology.context

topo = Topology("HelloWorld")
hw = topo.source(['hello', 'world', 2018])
hw.for_each(print)
streamsx.topology.context.submit("STANDALONE", topo.graph)

Operations such as source and sink accept a callable as input. The callable must be one of the following:

• the name of a built-in function
• the name of a function defined at the top level of a module
• an instance of a callable class defined at the top level of a module that implements the function __call__ and is picklable. Using a callable class allows state information such as user-defined parameters to be stored during class initialization and utilized when the instance is called.

The modules containing the callables, along with third-party libraries required by the modules, are copied into the Streams Application Bundle (sab file).

• Dependent libraries can be individual modules or packages.
• Dependent libraries can be installed in site packages, or not installed and simply reside in a directory in the Python search path
• Dependent native libaries outside of the package directory are not copied into the bundle

Limitations on callable inputs to operations:

• Importing modules that contain user-defined functions with importlib is unsupported. The PYTHONPATH or sys.path must contain the directory where modules to import are located.
• Importing modules that contain user-defined functions from zip/egg/wheel files is unsupported.