Variables

The bill of materials can contain a lot of information that is required by for analyses and there are a number of ways to access that information.

Examples notebook showing of using deifferent variables is here.

Parameters

The Parameter class aims to be the primary method for storing parameters within the Engineering Objects. A version (either Pint integrated or not) is included with every Engineering Object using the attribute params. The default is with Pint integration is set within the Config.

Having a structured method for storing parameters is key to sharing data - it allows additional information to be supplied such as the source or an improved description.

Individual parameters use namedtuple and the parameter database use DataFrames. In addition to the name and value that needs to be supplied to the individual parameter any futher information can be added as mentioned. If an additional bit of information is included (such as devaiation) all parameters will be updated with a empty placeholder for that information.

The design for parameter handling was inspired by BLUEPRINT (publication)

from bom_analysis import Q_
bolt.params.mass = Q_(0.1, "kg")
print(bolt.params.mass.to("g"))
>> "100 g"

See the bom_analysis.parameters.ParameterFrame for docstrings.

Assignment

An engineering object can be assigned values such as ‘Blanket’ or ‘Layer_2’ or ‘Yellow’ in order to provide additional information to analysis.

The aim of the assignment is to provide a list of strings that can be used in the calculation. For example, an engineering object may always want to be assigned the color “Yellow”.

Assignments are stored as numpy array but can be given a string as which the setter will add to the assignment.

bolt.assignment = "buttress thread"
bolt.assignment = "subsea yellow"
print(bolt.assignment)
>> np.array(["buttress thread", "subsea yellow"])

See the bom_analysis.bom.EngineeringObject.Assignment for docstrings.

Counting Parts

Multiples of the same part can be added to the bill of materials.

bolt_and_nut.add_component(nut)

bolt_and_nut.part_count("hex_nut")
>> 2

This will return and integer of 2 as there are 2 hex nuts in the assembly.

See the bom_analysis.bom.Assembly.part_count for docstrings.

Looking Up Variables

Variables can be extracted from the bill of materials parameters or any other attributes. All variable in all subcomponents of an assembly (and there subcomponents, to the lowest) will be extracted and a dictionary returned.

bolt_and_nut.lookup("material")
bolt_and_nut.lookup_params("mass")
>> {"P12345":{"mass":Q_(0.1, "kg")}}

See the bom_analysis.bom.Assembly.lookup_params for docstrings.

Accessing Nested

As a lot of BOM analysis can work with dictionaries, a function was included that allows extraction of a value from a heavily nested dictionary.

from bom_analysis.utils import access_nested
example = {"a":{"b"{"c"{"d":"e"}}}}
access_nested(example, ["a", "b", "c", "d"])
>> "e"

See the bom_analysis.utils.access_nested for docstrings.

Wrapped Dataframe

The DFClass is included in BOM analysis to allow for data to be stored in a dataframe but with some additional functionality.

This functionality includes printing with tabulate, reading and writing to a serialisable dictionary, and loading pint quantities.

See the bom_analysis.base.DFClass for docstrings.