Basic Algorithm Structure¶

Each Python algorithm within Mantid must contain a few elements in order for it to be recognised as an algorithm.

The basic layout should look like:

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

class HelloWorld(PythonAlgorithm):

    def PyInit(self):
        # Declare properties
        pass

    def PyExec(self):
        # Run the algorithm
        pass

# Register algorithm with Mantid
AlgorithmFactory.subscribe(HelloWorld)

The super class is PythonAlgorithm, which provides a hook to allow Mantid to interact with it without knowing about it beforehand.

The functions PyInit and PyExec are called by the framework to setup properties and run the algorithm respectively and must be included.

The final line, which should be outside the class definition, registers the new algorithm class with Mantid.

Each algorithm needs to belong to a category, by default a Python algorithm belongs to the “PythonAlgorithms”, but Mantid will emit a warning on registration if you leave it using the default value. To change this include the category() function in the definition, i.e.

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

class HelloWorld(PythonAlgorithm):

    def category(self):
        return 'MyTools'

   # The rest is the same as above

Subcategories can be defined using a “\\” (you need two \’s as the first is the escape character) to separate the categories. You can also state that your algorithm should appear in multiple categories by separating them with a semi-colon “;”.

i.e. The following code defines that the algorithm should be stored in Useful->Tools and MyTools.

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

class HelloWorld(PythonAlgorithm):

    def category(self):
        return 'Useful\\Tools;MyTools'

    # The rest is the same as above