Skip to content

python-api.md

Latest commit

 

History

History
98 lines (63 loc) · 1.6 KB

python-api.md

File metadata and controls

98 lines (63 loc) · 1.6 KB

Python Api

Public module surface

from qtty import Quantity, DerivedQuantity, DerivedUnit, Unit, UnitId

Unit is an alias for UnitId.

Quantity

Construction:

from qtty import Quantity, Unit

q = Quantity(42.0, Unit.Meter)

Properties:

  • q.value
  • q.unit

Main methods:

  • q.to(unit)
  • q.to_json()
  • Quantity.from_json(json_str)

Supported operators:

  • +, - between compatible quantities
  • * and / with scalars
  • / with another Quantity
  • unary +, unary -, abs(...)
  • comparisons between compatible quantities

Division behavior:

  • compatible dimensions return a Quantity ratio in the left operand unit
  • different dimensions return a DerivedQuantity

DerivedQuantity

Construction:

from qtty import DerivedQuantity, Unit

speed = DerivedQuantity(10.0, Unit.Meter, Unit.Second)

Properties:

  • value
  • numerator
  • denominator

Main methods:

  • symbol()
  • to(numerator, denominator)
  • to_json()
  • DerivedQuantity.from_json(json_str)

Supported operators:

  • * and / with scalars
  • unary -

DerivedUnit

DerivedUnit is a lightweight helper for a numerator and denominator pair.

from qtty import DerivedUnit, Unit

unit = DerivedUnit(Unit.Kilometer, Unit.Hour)
print(unit.symbol())

Error model

  • incompatible dimensions raise TypeError
  • division by zero raises ZeroDivisionError
  • unsupported operators raise TypeError or NotImplementedError

Serialization

Pickle works for:

  • Quantity
  • DerivedQuantity
  • UnitId

JSON helpers are provided on Quantity and DerivedQuantity.