LoopAlgorithmToPython

This Swift module uses LoopAlgorithm to create C functions for generating predictions and prediction dates from JSON data.

This is achieved by creating a foreign function interface (FFI) in Swift by using the unofficial @_cdecl Swift function. This interfaces the Swift code with C. Then we can create a dynamic library, import it into a Python (or other) repositories, and use for example ctypes to compile the C code.

Repository Overview

Exposed functions

You can find the C-exposed functions in the file Sources/LoopAlgorithmToPython/LoopAlgorithmToPython.swift.

Python API

Python API functions are located in loop_to_python_api/api.py.

Tests and test data

python_tests/ contains examples of executing all the functions as well as example files providing templates on how to structure the input files.

Python API Functions

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Initialize Exception Handlers

initialize_exception_handlers()

Initializes the exception and signal handlers in the Swift library to provide more informative error messages.

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Generate Prediction

generate_prediction(json_file, len=72)

Generates a prediction based on the provided JSON input.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
  • len (optional): The number of prediction values to generate. Defaults to 72.
• Returns: A list of prediction values.

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Get Prediction Dates

get_prediction_dates(json_file)

Fetches prediction dates based on the provided JSON input.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: A list of prediction dates as strings.

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Get Prediction Values and Dates

get_prediction_values_and_dates(json_file)

Combines the generate_prediction and get_prediction_dates functions to return both prediction values and dates.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: A tuple containing a list of prediction values and a list of prediction dates.

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Get Glucose Effect Velocity

get_glucose_effect_velocity(json_file, len=72)

Fetches the glucose effect velocity, which is equivalent to Insulin Counteraction Effect (ICE).

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
  • len (optional): The number of values to fetch. Defaults to 72.
• Returns: A list of glucose effect velocity values.

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Get Glucose Effect Velocity Dates

get_glucose_effect_velocity_dates(json_file)

Fetches the dates associated with the glucose effect velocity.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: A list of dates as strings.

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Get Glucose Velocity Values and Dates

get_glucose_velocity_values_and_dates(json_file)

Combines the get_glucose_effect_velocity and get_glucose_effect_velocity_dates functions to return both glucose effect velocity values and dates.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: A tuple containing a list of glucose effect velocity values and a list of dates.

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Get Active Carbs

get_active_carbs(json_file)

Fetches the active carbohydrates based on the provided JSON input.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: The active carbohydrates as a double.

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Get Active Insulin

get_active_insulin(json_file)

Fetches the active insulin based on the provided JSON input.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: The active insulin as a double.

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Percent Absorption at Percent Time

percent_absorption_at_percent_time(percent_time)

Calculates the percentage of carbohydrate absorption at a given percent time using a piecewise linear model.

• Parameters:
  • percent_time: The time as a fraction (e.g., 0.2 for 20%).
• Returns: The percentage of absorption as a double.

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Piecewise Linear Percent Rate at Percent Time

piecewise_linear_percent_rate_at_percent_time(percent_time)

Calculates the percentage rate of carbohydrate absorption at a given percent time using a piecewise linear model.

• Parameters:
  • percent_time: The time as a fraction (e.g., 0.2 for 20%).
• Returns: The percentage rate of absorption as a double.

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Linear Percent Rate at Percent Time

linear_percent_rate_at_percent_time(percent_time)

Calculates the percentage rate of carbohydrate absorption at a given percent time using a linear model.

• Parameters:
  • percent_time: The time as a fraction (e.g., 0.2 for 20%).
• Returns: The percentage rate of absorption as a double.

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Get Dynamic Carbs on Board

get_dynamic_carbs_on_board(json_file) Fetches the dynamic carbohydrates on board based on the provided JSON input.

• Parameters:
  • json_file: The JSON data input. See python tests and test files for example inputs.
• Returns: The dynamic carbohydrates on board as a double.

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Build Dynamic Library

The file python_api/libLoopAlgorithmToPython.dylib contains the dynamic library that is containing the C-embedded Swift functions.

After making changes in the Swift code, rebuild the dynamic library by running chmod +x build.sh followed by ./build.sh.

Run Tests

Run command pytest.

Debugging Advice

Debugging with this pipeline can be a pain... Calling functions with python does not give informative error messages, even though the initialize_exception_handlers() helps a little bit.

What I found the most useful is to go into LoopAlgorithm repository and run existing tests, but changing the input json files to the input json file that I am trying to use with this repository.