SPQ - Simple Physical Quantities

1.0.5 verified Sat May 09 auth: no python

A lightweight library for handling physical quantities with units and uncertainties. Version 1.0.5, semi-active development, sporadic releases.

pip install spq

Common errors

error ImportError: cannot import name 'Quantity' from 'spq' ↓

cause spq is not installed or imported from wrong module (e.g., spq.core).

fix

Install with pip install spq and import using from spq import Quantity.

error ValueError: Unknown unit symbol: 'meters' ↓

cause Using plural or non-standard unit strings.

fix

Use singular SI symbols: 'm' for meters, 'kg' for kilograms, etc.

Warnings

gotcha The 'Q' shorthand for creating quantities with uncertainties is undocumented in older versions. Use 'Quantity' constructor with uncertainty argument or 'Q' from spq. ↓

fix Use `from spq import Q` then `Q(value, uncertainty, unit)` or `Quantity(value, unit, uncertainty=...)`.

gotcha Unit string parsing is strict; unknown unit strings raise an error. Do not use plural or alternative spellings (e.g., 'meters' instead of 'm'). ↓

fix Always use SI base unit symbols (m, kg, s, A, K, mol, cd) or derived units (N, J, etc.).

deprecated The 'magnitude' attribute is deprecated in favor of 'value' in v1.0.5. ↓

fix Replace `q.magnitude` with `q.value`.

Imports

Quantity
```
from spq import Quantity
```
Can also use 'from spq import Q' as a shorthand
Unit
wrong
```
from spq.core import Unit
```
correct
```
from spq import Unit
```
Unit is exposed at package level, not from an internal module

Quickstart

Basic usage: create quantities with units, perform arithmetic, and convert units.

from spq import Quantity, Q

# Create a length with units
length = Quantity(5.0, 'm')
print(length)  # 5.0 m

# Arithmetic with automatic unit handling
area = length * length
print(area)  # 25.0 m^2

# Use Q shorthand for uncertainties
value = Q(10, 0.5, 'kg')  # 10 ± 0.5 kg
print(value)

# Unit conversion
print(length.to('cm'))  # 500.0 cm