PyomoUnitsContainer

(class from pyomo.core.base.units_container)

class pyomo.core.base.units_container.PyomoUnitsContainer(pint_registry=NOTSET)[source]

Bases: object

Class that is used to create and contain units in Pyomo.

This is the class that is used to create, contain, and interact with units in Pyomo. The module (pyomo.core.base.units_container) also contains a module level units container units that is an instance of a PyomoUnitsContainer. This module instance should typically be used instead of creating your own instance of a PyomoUnitsContainer. For an overview of the usage of this class, see the module documentation (pyomo.core.base.units_container)

This class is based on the “pint” module. Documentation for available units can be found at the following url: https://github.com/hgrecco/pint/blob/master/pint/default_en.txt

Note

Pre-defined units can be accessed through attributes on the PyomoUnitsContainer class; however, these attributes are created dynamically through the __getattr__ method, and are not present on the class until they are requested.

__init__(pint_registry=NOTSET)[source]: Create a PyomoUnitsContainer instance.

Methods

`__init__`([pint_registry])	Create a PyomoUnitsContainer instance.
`convert`(src[, to_units])	This method returns an expression that contains the explicit conversion from one unit to another.
`convert_temp_C_to_K`(value_in_C)	Convert a value in degrees Celsius to Kelvin Note that this method converts a numerical value only.
`convert_temp_F_to_R`(value_in_F)	Convert a value in degrees Fahrenheit to Rankine.
`convert_temp_K_to_C`(value_in_K)	Convert a value in Kelvin to degrees Celsius.
`convert_temp_R_to_F`(value_in_R)	Convert a value in Rankine to degrees Fahrenheit.
`convert_value`(num_value[, from_units, to_units])	This method performs explicit conversion of a numerical value from one unit to another, and returns the new value.
`get_units`(expr)	Return the Pyomo units corresponding to this expression (also performs validation and will raise an exception if units are not consistent).
`load_definitions_from_file`(definition_file)	Load new units definitions from a file
`load_definitions_from_strings`(...)	Load new units definitions from a string
`set_pint_registry`(pint_registry)

Attributes

pint_registry

Member Documentation

convert(src, to_units=None)[source]

This method returns an expression that contains the explicit conversion from one unit to another.

Parameters:

src (Pyomo expression) – The source value that will be converted. This could be a Pyomo Var, Pyomo Param, or a more complex expression.
to_units (Pyomo units expression) – The desired target units for the new expression

Returns:

ret

Return type:

Pyomo expression

convert_temp_C_to_K(value_in_C)[source]: Convert a value in degrees Celsius to Kelvin Note that this method converts a numerical value only. If you need temperature conversions in expressions, please work in absolute temperatures only.

convert_temp_F_to_R(value_in_F)[source]: Convert a value in degrees Fahrenheit to Rankine. Note that this method converts a numerical value only. If you need temperature conversions in expressions, please work in absolute temperatures only.

convert_temp_K_to_C(value_in_K)[source]: Convert a value in Kelvin to degrees Celsius. Note that this method converts a numerical value only. If you need temperature conversions in expressions, please work in absolute temperatures only.

convert_temp_R_to_F(value_in_R)[source]: Convert a value in Rankine to degrees Fahrenheit. Note that this method converts a numerical value only. If you need temperature conversions in expressions, please work in absolute temperatures only.

convert_value(num_value, from_units=None, to_units=None)[source]

This method performs explicit conversion of a numerical value from one unit to another, and returns the new value.

The argument “num_value” must be a native numeric type (e.g. float). Note that this method returns a numerical value only, and not an expression with units.

Parameters:

num_value (float or other native numeric type) – The value that will be converted
from_units (Pyomo units expression) – The units to convert from
to_units (Pyomo units expression) – The units to convert to

Returns:

float

Return type:

The converted value

get_units(expr)[source]

Return the Pyomo units corresponding to this expression (also performs validation and will raise an exception if units are not consistent).

Parameters:: expr (Pyomo expression) – The expression containing the desired units
Returns:: Returns the units corresponding to the expression
Return type:: Pyomo unit (expression)
Raises:: pyomo.core.base.units_container.UnitsError –

load_definitions_from_file(definition_file)[source]

Load new units definitions from a file

This method loads additional units definitions from a user specified definition file. An example of a definitions file can be found at: https://github.com/hgrecco/pint/blob/master/pint/default_en.txt

If we have a file called my_additional_units.txt with the following lines:

USD = [currency]

Then we can add this to the container with:

>>> u.load_definitions_from_file('my_additional_units.txt')
>>> print(u.USD)
USD

load_definitions_from_strings(definition_string_list)[source]

Load new units definitions from a string

This method loads additional units definitions from a list of strings (one for each line). An example of the definitions strings can be found at: https://github.com/hgrecco/pint/blob/master/pint/default_en.txt

For example, to add the currency dimension and US dollars as a unit, use

>>> u.load_definitions_from_strings(['USD = [currency]'])
>>> print(u.USD)
USD