CPython post-processing

RiskScape models support a post-processing script feature that can run a python script after your model finishes running. Your python script must declare a Python function in the following format, which will be the main entry-point for the Python script:

def function(metadata):
    pass

When called by RiskScape, it is given a single dictionary argument that contains metadata about the generated outputs as well as the parameters that were used to generate them.

A simple example might look like this:

[model impact-forecast]
framework = pipeline
location = impact-forecast-pipeline.txt
post-processing-script = ./functions/create-map-thumbnails.py

The CPython script will be called once your model completes successfully. Your script might look something like:

def function(metadata):
  for name, path in metadata['outputs'].items():
    # Assign a name for the output
    thumbnail_output = model_output('%s-thumbnail.jpg' % name)

    # Call our fancy thumbnailing method with the input path and the path where
    # RiskScape can expect to find it
    generate_map_thumbnail(path, thumbnail_output)

Metadata argument

The metadata argument is a JSON-like dictionary object containing:

• outputs: a dictionary of paths (or URIs if not stored locally) to the model’s outputs, keyed by the name that was assigned to the output, e.g. regional-impact

• parameters: a dictionary of the parameters that were used to build the model. Strings are given without quotes.

Registering model outputs

The model_output() function is a special Python function provided by RiskScape. It is usually called like this:

# example usage
with open(model_output('thumbnail.png'), 'w') as fout:
  pass # write something to fout

It tells RiskScape that our Python script is writing an output file (called thumbnail.png in our example above). RiskScape will make sure that file gets saved in the same directory as all the other model outputs.

Tip

We recommend that you use model_output() whenever you save a file in Python code. If you don’t, the file will still get written but it might end up in a different directory, and the model won’t be compatible with the RiskScape Platform.