Implement convert_value function

[adamnagel]

To work on this issue, create a new Git Branch called "issue-3".

In qudt4dt/init.py there is a function

def convert_value(self, source_unit_uri, destination_unit_uri, source_value)

Parameters:

• source_unit_uri: the URI of a Unit in the jena-fuseki database
• destination_unit_uri: the URI of a Unit in the jena-fuseki database
• source_value: a numerical value to be converted.

Return: The converted value. Assume that "source_value" has "source_unit_uri" as its Unit. Discover and perform the numerical conversion to find the new value with "destination_unit_uri" as the Unit.

Background Information

The QUDT ontology includes the information necessary to convert between units that share a unit class. Units include conversionOffset and conversionMultiplier fields that are used for this purpose.

Examples

• Kelvin
  • conversionMultiplier = 1.0
  • conversionOffset = 0.0
• DegreeCelcius
  • conversionMultiplier = 1.0
  • conversionOffset = 273.15
• DegreeFarenheit
  • conversionMultiplier = 0.5555555555555556
  • conversionOffset = 255.37037037037038

    Exceptions

In some cases, it will not be possible to convert between units. In these cases, a ValueError exception must be thrown.

• Units not in same class
  • If the two input Units are not in the same class, the function should return an exception. The conversion is not possible.
• Unit is missing conversionMultiplier or conversionOffset
  • The conversion will not be possible

    Unit Tests

Some unit tests should be implemented to verify that this function works correctly. Use Python's unittest package to build unit test functions. There should be functions that test correct operation, but there should also be assertRaises() tests to verify that exceptions are raised in the correct cases.

These tests should be implemented in the file test_qudt4dt.py in the repository. Refactor the tests in this file as a unit test class, and add new tests for convert_value.