metronos 0.1.1

A physical quantities and units package in Python.

Metronos

Metronos (from the Ancient Greek μέτρον /metron/, meaning "measure" or "that by which anything is measured.")

A lightweight Python library for physical quantities with units. No heavy dependencies, no mandatory annotations, no user-facing registries — just quantities that know what they are and refuse to let you mix them up.

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Installation

pip install git+https://github.com/cgburnsi/Metronos.git

Or clone and install locally:

git clone https://github.com/cgburnsi/Metronos.git
cd Metronos
pip install -e .

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Quick start

import metronos as mt

d = mt.Quantity(6.2, 'ft')
v = mt.Quantity(60, 'mile/s')
a = mt.Quantity(9.81, 'm/s^2')

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Features

Unit conversion

mt.Quantity(6.2, 'ft').to('m')          # Quantity(1.88976 [m])
mt.Quantity(60, 'mile/s').to('km/s')    # Quantity(96.56064 [km/s])
mt.Quantity(9.81, 'm/s^2').to('ft/s^2') # Quantity(32.185 [ft/s^2])

Arithmetic

Units combine automatically. Mixed-unit arithmetic works as long as the dimensions are compatible.

mt.Quantity(100, 'm') + mt.Quantity(0.5, 'km')   # Quantity(600.0 [m])

mass = mt.Quantity(70, 'kg')
accel = mt.Quantity(9.81, 'm/s^2')
force = mass * accel                              # Quantity(686.7 [m*kg/s^2])

KE = 0.5 * mass * mt.Quantity(10, 'm/s') ** 2   # Quantity(3500.0 [m^2*kg/s^2])

Temperature

Offset units (°C, °F, °R) are fully supported.

mt.Quantity(100, 'degC').to('degF')   # Quantity(212.0 [degF])
mt.Quantity(32, 'degF').to('K')       # Quantity(273.15 [K])

Extracting values

speed = mt.Quantity(25, 'm/s')
speed.to('km/s').value    # 0.025  (float, in the requested unit)

ratio = mt.Quantity(3.0) / mt.Quantity(1.5)
float(ratio)              # 2.0  (dimensionless quantities only)

Dimension safety

Metronos raises a DimensionError if you try to add or compare incompatible quantities.

mt.Quantity(1, 'm') + mt.Quantity(1, 'kg')   # DimensionError
mt.Quantity(1, 'm').to('s')                  # DimensionError
mt.Quantity(1, 'm') < mt.Quantity(1, 'kg')   # DimensionError

Comparisons

mt.Quantity(100, 'm') == mt.Quantity(0.1, 'km')   # True
mt.Quantity(100, 'm') < mt.Quantity(1, 'mile')    # True

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Supported units

SI base units

Symbol	Quantity
m	length
g	mass (base unit is kg internally)
s	time
A	electric current
K	temperature
mol	amount of substance
cd	luminous intensity

All SI base and derived units support the full prefix set (n, µ, m, k, M, G, etc.).

Derived SI units

Hz, N, Pa, J, W, C, V, Ω, S, F, T, Wb, H, lm, lx, Bq, Gy, Sv, kat, L

Customary US units

ft, in, inch, mile, yard, lb, lbf, psi, psia, gal, BTU, degF, degR

Other

bar, Torr, min, h, degC

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Philosophy

• Lean: No dependencies beyond the Python standard library.
• Pythonic: Clean, simple API with no mandatory annotations or boilerplate.
• Intuitive: It handles the dimensional math so you can focus on the physics.