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Array Properties

So far we have dealt with properties that contain a single item: int, float, string or workspace. In order to provide multiple items as input for a single property, i.e. a list of values, we must use a different type of property called an ArrayProperty.

While a Python list is capable of storing items of any type in the one list, the same is not true in C++. For this reason it is only possible for an array property to store a single type. This choice must be made when the property is declared. The options are:

• FloatArrayProperty - Stores a list of floats/doubles.

• IntArrayProperty - Stores a list of integers.

• StringArrayProperty - Stores a list of strings.

The simplest use of each is where the default value is empty:

def PyInit(self):
    self.declareProperty(FloatArrayProperty("Floats",
                                            direction=Direction.Input),
                                            doc='Input doubles')
    self.declareProperty(IntArrayProperty("Ints",
                                            direction=Direction.Input),
                                            doc='Input integers')
    self.declareProperty(StringArrayProperty("Strings",
                                            direction=Direction.Input),
                                            doc='Input strings')

Default values for the list can be specified as a python list, a numpy array or a comma-separated string using the values keyword.

def PyInit(self):
    self.declareProperty(FloatArrayProperty(name="PythonListInput",
                                            values=[1.2,4.5,6.7],
                                            direction=Direction.Input))

Validation

As with the other property types there is an option to supply a validator using the validator keyword. The available validators are:

• FloatArrayLengthValidator, IntArrayLengthValidator, StringArrayLengthValidator - Verify that the array is of a given length.

• FloatArrayBoundedValidator, IntArrayBoundedValidator - Verify that each value in the array is within the given bounds.

The prefix, Float, Int, String, must match the property type:

def PyInit(self):
    length_validator = FloatArrayLengthValidator(5)
    self.declareProperty(FloatArrayProperty("Floats",
                                            validator=length_validator,
                                            direction=Direction.Input))