Calling a Projection from a Python Script

Author: Guy Shepherd

In the last article I demonstrated how to run a Python script with arguments from a group projection task and return the results from the script back to

I will reverse the scenario and use a Python script to call a projection task in this example.  While the real-world use case for such a solution is perhaps less obvious, it may be useful for developers who are undertaking R&D or prototyping activity and wish to use an existing model together with a Python script as the basis for the work.

Environmental Configuration

The environment used for this example is identical to the previous example and again uses out-of-the-box installations of both Model Development Studio and Python:

  • Model Development Studio (Standard, Professional or Enterprise) v7.0 or later
  • Python 3.5 or later (64-bit edition preferred)

The Projection

This example uses the compile to EXE / DLL feature of Model Development Studio to create a Windows DLL from a given projection task.  This DLL is then called from the Python script as outlined in the steps below.

To keep things simple, I will generate a DLL from one of the sample projects included with Model Development Studio, but the same approach can be used for any project

To generate a projection DLL follow the steps below:

  1. Launch Model Development Studio
  2. Click New in the backstage menu
  3. Click Installed and then select the Sample Projects tab
  4. Now select Linked Funds Dynamic Basis from the list of available projects
  5. Give the project a suitable name – .e.g. LinkedFundsForPython and choose a folder in which to store the project – e.g. C:\ Projects\LinkedFundsForPython
  1. Click Create to create the project
  2. When the project opens navigate to the Tasks view
  3. Click on the Linked projection task
  4. Now select Create DLL / EXE from the Compile menu
  5. Click on the expand button to show the advanced options
  6. Select Projection DLL and enter a suitable location for the DLL to be created – e.g. C:\ Projects\LinkedFundsForPython\Linked_DLL
  7. Ensure that Merge Table Data is ticked
  8. Ensure that Target 64-bit is ticked (assuming the 64-bit version of Python is installed)
  1. Click OK to create the DLL

Before attempting to run the projection from Python, you will need to copy the Tables folder from: C:\ Projects\LinkedFundsForPython\

to… C:\ Projects\LinkedFundsForPython\Linked_DLL. 

After this step there should be a number of files in:

C:\ Projects\LinkedFundsForPython\Linked_DLL\Tables

We are now in a position to call the projection DLL from Python.

Python Script

The script below illustrates how to call the projection DLL created above, overriding a projection parameter and retrieving a result from the projection.  This script can be saved as a .py file (or copied into a Python IDE, such as IDLE or PyCharm) and run.

import sys
import clr

# define path to the Linked DLL and add this to system path

assembly_path = r"C:\ Projects\LinkedFundsForPython\Linked_DLL"

# add kernel assembly references to the CLR


# add projection DLL reference to the CLR

clr_ref = clr.AddReference("Linked_Monet")
monet_type = clr_ref.GetType('Monet')

# invoke interface methods

initCmdLine_method = monet_type.GetMethod('InitCommandLine')
initCmdLine_method.Invoke(None, [None])

init_method = monet_type.GetMethod('Initialise')
init_method.Invoke(None, [True])

initProj_method = monet_type.GetMethod('InitialiseProjections')
initProj_method.Invoke(None, [])

# obtain a list of the projections inside the DLL

projections = monet_type.GetProperty('Projections')

# create a reference to the Linked projection task

linkedproj = projections.GetValue(None).Linked

# uncomment the next line to override the SterlInt parameter associated with the
# Linked projection

# linkedproj.SterlInt = 0.1

# run the projection


# show the sterling result at time=0 

print(f'SterlInt = {linkedproj.SterlInt}')
print(f'SterlRes(0) = {linkedproj.SterlRes(0)}')

When the script is run for the first time, the following results should be shown in the console.

SterlInt = 0.03
SterlRes(0) = -3310.1472717414354

Removing the comment from line 41 in the script will override the SterlInt parameter.  Re-running the script should then show the following results:

SterlInt = 0.1
SterlRes(0) = -1673.3090454761546

Other projection parameters can be overridden in a similar way.

What’s Going On?

The key elements of the Python script are as follows.

6This defines the location of the DLL.  The path should be changed to reflect the location of DLL on the user’s environment.
11-12These are two of the kernel assemblies that the common language runtime needs to know about
16This creates a reference to the DLL itself.  This is the name of the DLL found in the path defined at line 6
17This defines the monet_type, which is used to invoke specific methods
21-22This invokes the command line interface
24-25This invokes the initialise method
27-28This invokes the initialise projections method
32This gets a list of the projections inside the DLL
36Creates a reference to the Linked projection task
41Uncomment this line to override the SterlInt parameter associated with the Linked projection task
45This runs the projection
49-50This prints the overridden SterlInt parameter (to confirm it has been correctly passed to the projection), and the calculated value of the sterling reserve (SterlRes) at time 0 to the console


I hope this series of articles has helped to demonstrate how and Python can complement each other and allow users to develop comprehensive modelling solutions which leverage the features from both platforms without the need to refactor anything.

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