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Exercise 2 Solutions

The aim of this exercise is to write a small Python algorithm that is able to print to the Messages Box the first n numbers of the Fibonacci series. The series starts with 0, 1 and then the next term is the sum of the two previous terms.

# Extending Mantid With Python: Exercise 2
#
# The algorithm should:
#  - Define a property that sets the maximum number of terms to print. Single letters are not considered good property names so a good name
#    would be something like NTerms
#  - The property should have documentation that shows in the GUI describing what it is used for.
#  - Validate that NTerms property is greater or equal to 1 when set in the GUI.
#  - The log message for the value of each term should be at notice level and in the format: "Term 1 in the Fibonacci series is: 0"
#  - Add log message at debug level that prints the value of the NTerms property after it has been retrieved.
#
# As an additional exercise in understanding errors:
# - On execution, check that the value of NTerms is less than or equal to 1000. If it is not then raise a RuntimeError.

from mantid.kernel import *
from mantid.api import *

class FibonacciExercise(PythonAlgorithm):

    def category(self):
        return "Examples"

    def PyInit(self):
        self.declareProperty(name="NTerms", defaultValue=-1, validator=IntBoundedValidator(lower=0), doc="Number of terms to print")

    def PyExec(self):
        nterms = self.getProperty("NTerms").value
        self.log().debug("NTerms = " + str(nterms))

        if nterms > 1000:
            raise RuntimeError("Number of terms greater than 1000")

        # 0 should print something else
        if nterms < 1:
            msg = "Number of terms selected less than 1"
        else:
            # First two terms
            prev_2, prev_1 = 0, 1

            msg = "Term 1 in the Fibonacci series is: " + str(prev_2) + "\n"
            msg += "Term 2 in the Fibonacci series is: " + str(prev_1) + "\n"
            count = 2
            while count < nterms:
                count += 1
                current = prev_2 + prev_1
                msg += "Term " + str(count) + " in the Fibonacci series is: " + str(current) + "\n"
                prev_2 = prev_1
                prev_1 = current
        # End of else

        # Display whole log message in single shot
        self.log().notice(msg)

# Register algorithm with mantid
AlgorithmFactory.subscribe(FibonacciExercise)