encomp 1.5.2

General-purpose library for engineering calculations

encomp

General-purpose library for engineering computations.

encomp is tested on Windows, Linux, and macOS, with Python 3.13 and 3.14.

Overview

Every physical quantity in encomp carries a magnitude, a unit, and a dimensionality. The dimensionality is a type that both static checkers and the runtime understand.

• Quantity (encomp.units, encomp.utypes) extends pint: each dimensionality (pressure, mass flow, density, ...) is a distinct subclass of Quantity. Dividing a Mass by a Volume gives a Density, inferred by static type checkers and verified at runtime. Magnitudes can be scalars, NumPy arrays, Polars Series, or Polars Expr.

• Static unit checking. Common dimensionalities and their * / / / ** combinations are encoded as __new__ overloads, so a type checker flags a Temperature passed where a Power is expected. @typeguard.typechecked extends the same checks to runtime.

• Fluid / Water / HumidAir (encomp.fluids) wrap CoolProp: fix a state with two points (three for humid air) and read any property as an attribute. Inputs and outputs are Quantity objects, so units are converted and validated automatically.

• CoolProp as Polars expressions (encomp.coolprop). Properties evaluate as native Polars expression plugins written in Rust, so independent properties in one select / with_columns run in parallel without holding the GIL. See Parallel CoolProp evaluation with Polars.

• Symbolic math with units (encomp.sympy) extends Sympy: typeset sub- and superscripts, convert expressions or systems to NumPy functions, combine quantities directly with symbols.

• Serialization and settings. Quantity fields work as Pydantic model types (JSON round-trip, dimensionality validation). Library behavior is configured from an .env file.

The remaining modules (encomp.gases, encomp.conversion, encomp.constants, ...) implement process-engineering and thermodynamics calculations.

Installation

pip install encomp

encomp ships as a single per-platform wheel that bundles the compiled Rust plugin and the CoolProp shared library, so there is nothing to build. For a development checkout, see Tests.

The Quantity class

encomp.units.Quantity (alias Q) extends pint.Quantity. A quantity has a magnitude and a unit; each unit has a dimensionality (a combination of the base dimensions), and each dimensionality has multiple associated units.

from encomp.units import Quantity as Q

# convert 1 bar to kPa
Q(1, "bar").to("kPa")

# list inputs are converted to np.ndarray
Q([1, 2, 3], "bar") * 2  # [2, 4, 6] bar

# without a unit, the quantity is dimensionless
assert Q(0.1) == Q(10, "%")

Quantity type system

Each Quantity has a Dimensionality type parameter, determined at runtime from the unit. Each dimensionality (for example pressure, length, time, dimensionless) is a subclass of Quantity.

For registered units (see encomp.utypes.get_registered_units), the dimensionality is also inferred statically, via overloads of Quantity.__new__. The *, / and ** operations between the default dimensionalities are overloaded as well. When the dimensionality cannot be inferred, the static type falls back to UnknownDimensionality; the runtime dimensionality is always evaluated from the unit.

The dimensionality can also be given explicitly, using a subclass of encomp.utypes.Dimensionality as the type parameter.

Common dimensionalities are defined in the encomp.utypes module. A newly created dimensionality gets a class name of the form Dimensionality[...] (for example Quantity[Dimensionality[[mass] ** 2 / [length] ** 3]]).

# test: no-run

from encomp.units import Quantity as Q
from encomp.utypes import MassFlow, Volume

# the types are inferred by a static type checker

# the unit "kg" is registered as a Mass unit
m = Q(12, "kg")  # Quantity[Mass, float]

V = Q(25, "liter")  # Quantity[Volume, float]

# common / and * operations are encoded as overloads
rho = m / V  # Quantity[Density, float]

# the unit "kg/week" is not registered by default
# the individual units "kg" and "week" are registered, however
# the type checker does not know how to combine these units
m_ = Q(25, "kg/week")  # Quantity[UnknownDimensionality, float]

# at runtime, the dimensionality of m_ will be evaluated to MassFlow
isinstance(m_, Q[MassFlow])  # True

# these operations (Mass**2 divided by Volume) are not explicitly defined as overloads
# at runtime, the type will be evaluated to
# Quantity[Dimensionality[[mass] ** 2 / [length] ** 3]]
x = m**2 / V  # Quantity[UnknownDimensionality, float]

# the unit name "meter cubed" is not defined using an overload
y = Q(15, "meter cubed").asdim(Volume)  # Quantity[Volume, float]

# if the explicit dimensionality does not match
# the unit, an error is raised at runtime

y = Q(15, "meter cubed").asdim(MassFlow)
# ExpectedDimensionalityError: Cannot convert 15.0 m³ to dimensionality
# <class 'encomp.utypes.MassFlow'>, the dimensions do not match:
# [length] ** 3 != [mass] / [time]

Runtime type checking

The Quantity subtypes also restrict function and class attribute types at runtime. The typeguard.typechecked decorator checks function inputs and outputs:

# test: no-run

from typing import Any, TypedDict

from typeguard import typechecked

from encomp.units import Quantity as Q
from encomp.utypes import Length, Pressure, Temperature


@typechecked
def some_func(T: Q[Temperature, float]) -> tuple[Q[Length, float], Q[Pressure, float]]:
    return (T * Q(12.4, "m/K")).asdim(Length), Q(1, "bar")


some_func(Q(12, "K"))  # the dimensionalities check out
some_func(Q(26, "kW"))  # raises an exception:
# TypeCheckError: argument "T" (encomp.units.Quantity[Power, float])
# is not an instance of encomp.units.Quantity[Temperature, float]


class OutputDict(TypedDict):
    P: Q[Pressure, Any]
    T: Q[Temperature, Any]


@typechecked
def another_func(_s: Q[Length, Any]) -> OutputDict:
    return {"T": Q(25, "m"), "P": Q(25, "kPa")}


another_func(Q(25, "m"))
# TypeCheckError: value of key 'T' of the return value (dict)
# is not an instance of encomp.units.Quantity[Temperature]

To create a new dimensionality (for example temperature difference per mass flow rate), combine the pint.UnitsContainer objects stored in the dimensions class attribute.

import contextlib

from encomp.units import DimensionalityError
from encomp.units import Quantity as Q
from encomp.utypes import Dimensionality, MassFlow, TemperatureDifference


# the class name TemperaturePerMassFlow must be globally unique
class TemperaturePerMassFlow(Dimensionality):
    dimensions = TemperatureDifference.dimensions / MassFlow.dimensions


# note the extra parentheses around (kg/s)
qty = Q(1, "delta_degC/(kg/s)").asdim(TemperaturePerMassFlow)

# raises an exception since liter is Length**3 and the Quantity expects Mass
with contextlib.suppress(DimensionalityError):
    Q(1, "delta_degC/(liter/hour)").asdim(TemperaturePerMassFlow)

# create a new subclass of Quantity with restricted input units
CustomCoolingCapacity = Q[TemperaturePerMassFlow, float]

# the pint library handles a wide range of input formats and unit names
# the prefix "delta_" can be omitted in this case
q1 = CustomCoolingCapacity(6, "°F per (lbs per week)")
q2 = Q(3, "delta_degF per (pound per fortnight)")

assert q1 == q2
assert type(q1) is type(q2)

The Fluid class

encomp.fluids.Fluid wraps the CoolProp library. Two input points (three for humid air) fix the state of the fluid; any other property is read as an attribute. Inputs and outputs are Quantity objects. Property names follow CoolProp; use the .search() method to find them.

from encomp.fluids import Fluid
from encomp.units import Quantity as Q

air = Fluid("air", T=Q(25, "degC"), P=Q(2, "bar"))

# common fluid properties have type hints, and show up using autocomplete
density = air.D  # 2.338399526231983 kg/m³

air.search("density")
# ['DELTA, Delta: Reduced density (rho/rhoc) [dimensionless]',
#  'DMOLAR, Dmolar: Molar density [mol/m³]',
#  'D, DMASS, Dmass: Mass density [kg/m³]', ...

# any of the names are valid attributes (case-sensitive)
molar_density = air.Dmolar  # 80.73061937328056 mol/m³

The Water subclass (and Fluid("IF97::Water")) evaluates steam and water properties with IAPWS-IF97 (Industrial Formulation 1997). For the IAPWS-95 reference formulation, use the HEOS backend: Fluid("HEOS::Water", ...); the bare name Fluid("water", ...) also resolves to HEOS.

from encomp.fluids import Fluid, Water
from encomp.units import Quantity as Q

Fluid("water", P=Q(25, "bar"), T=Q(550, "°C"))
# <Fluid "water", P=2500 kPa, T=550.0 °C, D=6.7 kg/m³, V=0.031 cP>

# note that the CoolProp property "Q" (vapor quality) has the same name as the class
# the Water class has a slightly different string representation
Water(Q=Q(0.5), T=Q(170, "degC"))
# <Water (Two-phase), P=792 kPa, T=170.0 °C, D=8.2 kg/m³, V=nan cP>

Water(H=Q(2800, "kJ/kg"), S=Q(7300, "J/kg/K"))
# <Water (Gas), P=225 kPa, T=165.8 °C, D=1.1 kg/m³, V=0.0 cP>

Mixtures are given either by fractions folded into the name or by a composition dict of mole fractions. Use assume_phase to skip CoolProp's phase-stability search when the phase is known; that search dominates the cost for the HEOS/GERG mixture backends.

from encomp.fluids import Fluid
from encomp.units import Quantity as Q

# equivalent: fractions in the name, or a composition dict
Fluid("HEOS::CO2[0.7]&O2[0.3]", P=Q(10, "bar"), T=Q(300, "K"))
Fluid("HEOS", P=Q(10, "bar"), T=Q(300, "K"), composition={"CO2": 0.7, "O2": 0.3}).assume_phase("gas")

The HumidAir class requires three input points (R means relative humidity):

from encomp.fluids import HumidAir
from encomp.units import Quantity as Q

HumidAir(P=Q(1, "bar"), T=Q(100, "degC"), R=Q(0.5))
# <HumidAir, P=100 kPa, T=100.0 °C, R=0.50, Vda=2.2 m³/kg, Vha=1.3 m³/kg, M=0.017 cP>

Parallel CoolProp evaluation with Polars

CoolProp property evaluation is exposed as native Polars expression plugins (Rust, over the CoolProp C-API). Independent property nodes in one select / with_columns / collect(), eager or lazy, are evaluated in parallel on the Polars thread pool without holding the GIL (a Python map_batches UDF re-acquires the GIL per batch and serializes).

Fluid properties accept Quantity-wrapped Polars expressions (pl.Expr) and return a pl.Expr:

import polars as pl

from encomp.fluids import Water
from encomp.units import Quantity as Q

df = pl.DataFrame({"P": [50e5, 60e5], "T": [400.0, 450.0]})  # Pa, K
w = Water(P=Q(pl.col("P"), "Pa"), T=Q(pl.col("T"), "K"))

# these independent CoolProp properties run in parallel across cores
df.select(w.D.m.alias("rho"), w.H.m.alias("h"), w.S.m.alias("s"))

pl.Expr (lazy) inputs are evaluated exclusively through the plugin (there is no map_batches fallback). Eager float / NumPy / pl.Series inputs use the Python CoolProp path, except arrays of at least EAGER_PLUGIN_MIN_SIZE (1000) elements, which also route through the plugin. The two paths are verified to agree on value, NaN/null handling, and dtype; results are bit-identical when the installed coolprop matches the bundled build (8.0.0).

The plugin is also usable directly on any Polars expression, independent of the Fluid class (the encomp.coolprop package):

import polars as pl

from encomp import coolprop as cp

df = pl.DataFrame({"P": [1e5, 1e5], "T": [293.15, 313.15], "R": [0.4, 0.6]})  # Pa, K, -

df.select(
    cp.fluid("DMASS", "P", "T").alias("rho"),  # default: IF97 water
    cp.fluid("HMASS", "P", "T").alias("h"),
    cp.humid_air("W", "P", "T", "R").alias("humidity_ratio"),
)
# mirrors encomp.fluids: any CoolProp input pair (in any order), the fluid via
# name='HEOS::CarbonDioxide', mixtures via a composition={species: mole fraction}
# dict, and a fixed phase via assume_phase='gas'

Implementation

The GIL is not the only serialization point: the CoolProp C-API takes a global handle-table lock on every call, so per-row calls serialize even in Rust. The plugin uses the batched C-API (AbstractState_update_and_1_out): one call per chunk, the handle lock taken once at construction, then the flash loop runs lock-free in C++. Independent chunks and independent property expressions parallelize.

Benchmarks (CoolProp 8.0, 14-thread pool):

workload	vs map_batches	notes
single property D, 1M rows	~2.1x	also ~2x faster than vectorized PropsSI
4 independent properties, one collect(), 1M rows	~4.6x	map_batches is serial on the GIL; the plugin runs ~4 cores
8 enthalpy calculations, 1M rows	~4.9x	~6 cores vs 1, roughly half the peak memory

Each fluid(...) / humid_air(...) is an independent plugin node, so selecting K properties of one state runs K flashes of it — Polars cannot reuse the shared flash across opaque plugin nodes. Independent properties still parallelize, so this is total work, not wall-clock. See encomp/coolprop/README.md for the design, thread-safety model, and caveats.

Symbolic math

To load additional methods for the sympy.Symbol class, import Sympy via the encomp.sympy module. The _ / __ methods add typeset sub- and superscripts, and quantities combine directly with symbols:

from encomp.sympy import sp
from encomp.units import Quantity as Q

n = sp.Symbol("n", integer=True)
n._("H_2O").__("out")  # n_{\text{H}_2\text{O}}^{\text{out}}, keeps the integer assumption

x, y, z = sp.symbols("x, y, z")
result_expr = (25 * x * y / z).subs({x: Q(235, "yard"), y: Q(2, "m²"), z: Q(0.4, "m³/kg")})
Q.from_expr(result_expr)  # 26860.5 kg

For array magnitudes, convert the expression to a NumPy-aware function with encomp.sympy.get_function.

Tests

Install the development dependencies with uv sync --all-extras --all-groups, then run

pytest

Settings

The attributes of encomp.settings.Settings are overridden with a file named .env in the current working directory. Attribute names are prefixed with ENCOMP_.

Documentation

The usage guide, example notebooks, and API reference are at encomp.readthedocs.io.