Base API

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Base API#

These are the classes, exceptions and functions that you will most likely use.

Most important classes#

class pint.UnitRegistry(*args: Any, **kwargs: Any)[source]#

The unit registry stores the definitions and relationships between units.

Parameters:

  • filename – path of the units definition file to load or line-iterable object. Empty string to load the default definition file. (default) None to leave the UnitRegistry empty.

  • force_ndarray (bool) – convert any input, scalar or not to a numpy.ndarray. (Default: False)

  • force_ndarray_like (bool) – convert all inputs other than duck arrays to a numpy.ndarray. (Default: False)

  • default_as_delta – In the context of a multiplication of units, interpret non-multiplicative units as their delta counterparts. (Default: False)

  • autoconvert_offset_to_baseunit – If True converts offset units in quantities are converted to their plain units in multiplicative context. If False no conversion happens. (Default: False)

  • on_redefinition (str) – action to take in case a unit is redefined. ‘warn’, ‘raise’, ‘ignore’ (Default: ‘raise’)

  • auto_reduce_dimensions – If True, reduce dimensionality on appropriate operations. (Default: False)

  • autoconvert_to_preferred – If True, converts preferred units on appropriate operations. (Default: False)

  • preprocessors – list of callables which are iteratively ran on any input expression or unit string or None for no preprocessor. (Default=None)

  • fmt_locale – locale identifier string, used in format_babel or None. (Default=None)

  • case_sensitive (bool, optional) – Control default case sensitivity of unit parsing. (Default: True)

  • cache_folder (str or pathlib.Path or None, optional) – Specify the folder in which cache files are saved and loaded from. If None, the cache is disabled. (default)

check(*args: str | UnitsContainer | Unit | None) → Callable[[F], F]#

Decorator to for quantity type checking for function inputs.

Use it to ensure that the decorated function input parameters match the expected dimension of pint quantity.

The wrapper function raises:

  • pint.DimensionalityError if an argument doesn’t match the required dimensions.

uregUnitRegistry

a UnitRegistry instance.

argsstr or UnitContainer or None

Dimensions of each of the input arguments. Use None to skip argument conversion.

Returns:

callable() – the wrapped function.

Raises:

  • TypeError – If the number of given dimensions does not match the number of function parameters.

  • ValueError – If the any of the provided dimensions cannot be parsed as a dimension.

pi_theorem(quantities)[source]#

Builds dimensionless quantities using the Buckingham π theorem

Parameters:

quantities (dict) – mapping between variable name and units

Returns:

list – a list of dimensionless quantities expressed as dicts

setup_matplotlib(enable: bool = True) → None[source]#

Set up handlers for matplotlib’s unit support.

Parameters:

enable (bool) – whether support should be enabled or disabled (Default value = True)

wraps(ret: str | Unit | Iterable[str | Unit | None] | None, args: str | Unit | Iterable[str | Unit | None] | None, strict: bool = True) → Callable[[Callable[..., Any]], Callable[..., Quantity]]#

Wraps a function to become pint-aware.

Use it when a function requires a numerical value but in some specific units. The wrapper function will take a pint quantity, convert to the units specified in args and then call the wrapped function with the resulting magnitude.

The value returned by the wrapped function will be converted to the units specified in ret.

Parameters:
Returns:

callable() – the wrapper function.

Raises:

TypeError – if the number of given arguments does not match the number of function parameters. if any of the provided arguments is not a unit a string or Quantity

class pint.Quantity(value: MagnitudeT, units: UnitLike | None = None)[source]#
class pint.Quantity(value: str, units: UnitLike | None = None)
class pint.Quantity(value: Sequence[ScalarT], units: UnitLike | None = None)
class pint.Quantity(value: PlainQuantity[Any], units: UnitLike | None = None)
check(dimension: str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit) → bool#

Return true if the quantity’s dimension matches passed dimension.

compute(**kwargs)#

Compute the Dask array wrapped by pint.PlainQuantity.

Parameters:

**kwargs (dict) – Any keyword arguments to pass to dask.compute.

Returns:

pint.PlainQuantity – A pint.PlainQuantity wrapped numpy array.

property dimensionality: UnitsContainerT#
Returns:

dict – Dimensionality of the PlainQuantity, e.g. {length: 1, time: -1}

dot(b)#

Dot product of two arrays.

Wraps np.dot().

classmethod from_list(quant_list: list[PlainQuantity[MagnitudeT]], units=None) → PlainQuantity[MagnitudeT]#

Transforms a list of Quantities into an numpy.array quantity. If no units are specified, the unit of the first element will be used. Same as from_sequence.

If units is not specified and list is empty, the unit cannot be determined and a ValueError is raised.

Parameters:

  • quant_list (list of pint.PlainQuantity) – list of pint.PlainQuantity

  • units (UnitsContainer, str or pint.PlainQuantity) – units of the physical quantity to be created (Default value = None)

Returns:

pint.PlainQuantity

classmethod from_sequence(seq: Sequence[PlainQuantity[MagnitudeT]], units=None) → PlainQuantity[MagnitudeT]#

Transforms a sequence of Quantities into an numpy.array quantity. If no units are specified, the unit of the first element will be used.

If units is not specified and sequence is empty, the unit cannot be determined and a ValueError is raised.

Parameters:

  • seq (sequence of pint.PlainQuantity) – sequence of pint.PlainQuantity

  • units (UnitsContainer, str or pint.PlainQuantity) – units of the physical quantity to be created (Default value = None)

Returns:

pint.PlainQuantity

is_compatible_with(other: Any, *contexts: str | Context, **ctx_kwargs: Any) → bool#

check if the other object is compatible

Parameters:

  • other – The object to check. Treated as dimensionless if not a PlainQuantity, Unit or str.

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

Returns:

bool

ito(other: Quantity | str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit | None = None, *contexts, **ctx_kwargs) → None#

Inplace rescale to different units.

Parameters:

  • other (pint.PlainQuantity, str or dict) – Destination units. (Default value = None)

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

ito_base_units() → None#

Return PlainQuantity rescaled to plain units.

ito_preferred(preferred_units: list[UnitLike] | None = None) → PlainQuantity#

Return Quantity converted to a unit composed of the preferred units.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (1*ureg.acre).to_preferred([ureg.meters])
<Quantity(4046.87261, 'meter ** 2')>
>>> (1*(ureg.force_pound*ureg.m)).to_preferred([ureg.W])
<Quantity(4.44822162, 'watt * second')>
ito_reduced_units() → None#

Return PlainQuantity scaled in place to reduced units, i.e. one unit per dimension. This will not reduce compound units (e.g., ‘J/kg’ will not be reduced to m**2/s**2), nor can it make use of contexts at this time.

ito_root_units() → None#

Return PlainQuantity rescaled to root units.

property m: MagnitudeT#

PlainQuantity’s magnitude. Short form for magnitude

m_as(units) → MagnitudeT#

PlainQuantity’s magnitude expressed in particular units.

Parameters:

units (pint.PlainQuantity, str or dict) – destination units

property magnitude: MagnitudeT#

PlainQuantity’s magnitude. Long form for m

persist(**kwargs)#

Persist the Dask Array wrapped by pint.PlainQuantity.

Parameters:

**kwargs (dict) – Any keyword arguments to pass to dask.persist.

Returns:

pint.PlainQuantity – A pint.PlainQuantity wrapped Dask array.

prod(axis=None, dtype=None, out=None, keepdims=<no value>, initial=<no value>, where=<no value>)#

Return the product of quantity elements over a given axis

Wraps np.prod().

to(other: Quantity | str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit | None = None, *contexts, **ctx_kwargs) → PlainQuantity#

Return PlainQuantity rescaled to different units.

Parameters:

  • other (pint.PlainQuantity, str or dict) – destination units. (Default value = None)

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

Returns:

pint.PlainQuantity

to_base_units() → PlainQuantity[MagnitudeT]#

Return PlainQuantity rescaled to plain units.

to_compact(unit: UnitsContainer | None = None) → PlainQuantity#

“Return PlainQuantity rescaled to compact, human-readable units.

To get output in terms of a different unit, use the unit parameter.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (200e-9*ureg.s).to_compact()
<Quantity(200.0, 'nanosecond')>
>>> (1e-2*ureg('kg m/s^2')).to_compact('N')
<Quantity(10.0, 'millinewton')>
to_preferred(preferred_units: list[UnitLike] | None = None) → PlainQuantity#

Return Quantity converted to a unit composed of the preferred units.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (1*ureg.acre).to_preferred([ureg.meters])
<Quantity(4046.87261, 'meter ** 2')>
>>> (1*(ureg.force_pound*ureg.m)).to_preferred([ureg.W])
<Quantity(4.44822162, 'watt * second')>
to_reduced_units() → PlainQuantity#

Return PlainQuantity scaled in place to reduced units, i.e. one unit per dimension. This will not reduce compound units (intentionally), nor can it make use of contexts at this time.

to_root_units() → PlainQuantity[MagnitudeT]#

Return PlainQuantity rescaled to root units.

property u: Unit#

PlainQuantity’s units. Short form for units

unit_items() → Iterable[tuple[str, float | int | Decimal | Fraction]]#

A view of the unit items.

property units: Unit#

PlainQuantity’s units. Long form for u

visualize(**kwargs)#

Produce a visual representation of the Dask graph.

The graphviz library is required.

Parameters:

**kwargs (dict) – Any keyword arguments to pass to dask.visualize.

class pint.Unit(*args, **kwargs)[source]#
property dimensionality: UnitsContainer#
Returns:

dict – Dimensionality of the PlainUnit, e.g. {length: 1, time: -1}

property dimensionless: bool#

Return True if the PlainUnit is dimensionless; False otherwise.

from_(value, strict=True, name='value')#

Converts a numerical value or quantity to this unit

Parameters:

  • value – a Quantity (or numerical value if strict=False) to convert

  • strict – boolean to indicate that only quantities are accepted (Default value = True)

  • name – descriptive name to use if an exception occurs (Default value = “value”)

Returns:

type – The converted value as this unit

is_compatible_with(other: Any, *contexts: str | Context, **ctx_kwargs: Any) → bool#

check if the other object is compatible

Parameters:

  • other – The object to check. Treated as dimensionless if not a Quantity, PlainUnit or str.

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

Returns:

bool

m_from(value, strict=True, name='value')#

Converts a numerical value or quantity to this unit, then returns the magnitude of the converted value

Parameters:

  • value – a Quantity (or numerical value if strict=False) to convert

  • strict – boolean to indicate that only quantities are accepted (Default value = True)

  • name – descriptive name to use if an exception occurs (Default value = “value”)

Returns:

type – The magnitude of the converted value

class pint.Measurement(value, error=<object object>, units=<object object>)[source]#

Implements a class to describe a quantity with uncertainty.

Parameters:

  • value (pint.Quantity or any numeric type) – The expected value of the measurement

  • error (pint.Quantity or any numeric type) – The error or uncertainty of the measurement

check(dimension: str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit) → bool#

Return true if the quantity’s dimension matches passed dimension.

property dimensionality: UnitsContainerT#
Returns:

dict – Dimensionality of the PlainQuantity, e.g. {length: 1, time: -1}

classmethod from_list(quant_list: list[PlainQuantity[MagnitudeT]], units=None) → PlainQuantity[MagnitudeT]#

Transforms a list of Quantities into an numpy.array quantity. If no units are specified, the unit of the first element will be used. Same as from_sequence.

If units is not specified and list is empty, the unit cannot be determined and a ValueError is raised.

Parameters:

  • quant_list (list of pint.PlainQuantity) – list of pint.PlainQuantity

  • units (UnitsContainer, str or pint.PlainQuantity) – units of the physical quantity to be created (Default value = None)

Returns:

pint.PlainQuantity

classmethod from_sequence(seq: Sequence[PlainQuantity[MagnitudeT]], units=None) → PlainQuantity[MagnitudeT]#

Transforms a sequence of Quantities into an numpy.array quantity. If no units are specified, the unit of the first element will be used.

If units is not specified and sequence is empty, the unit cannot be determined and a ValueError is raised.

Parameters:

  • seq (sequence of pint.PlainQuantity) – sequence of pint.PlainQuantity

  • units (UnitsContainer, str or pint.PlainQuantity) – units of the physical quantity to be created (Default value = None)

Returns:

pint.PlainQuantity

is_compatible_with(other: Any, *contexts: str | Context, **ctx_kwargs: Any) → bool#

check if the other object is compatible

Parameters:

  • other – The object to check. Treated as dimensionless if not a PlainQuantity, Unit or str.

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

Returns:

bool

ito(other: Quantity | str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit | None = None, *contexts, **ctx_kwargs) → None#

Inplace rescale to different units.

Parameters:

  • other (pint.PlainQuantity, str or dict) – Destination units. (Default value = None)

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

ito_base_units() → None#

Return PlainQuantity rescaled to plain units.

ito_preferred(preferred_units: list[UnitLike] | None = None) → PlainQuantity#

Return Quantity converted to a unit composed of the preferred units.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (1*ureg.acre).to_preferred([ureg.meters])
<Quantity(4046.87261, 'meter ** 2')>
>>> (1*(ureg.force_pound*ureg.m)).to_preferred([ureg.W])
<Quantity(4.44822162, 'watt * second')>
ito_reduced_units() → None#

Return PlainQuantity scaled in place to reduced units, i.e. one unit per dimension. This will not reduce compound units (e.g., ‘J/kg’ will not be reduced to m**2/s**2), nor can it make use of contexts at this time.

ito_root_units() → None#

Return PlainQuantity rescaled to root units.

property m: MagnitudeT#

PlainQuantity’s magnitude. Short form for magnitude

m_as(units) → MagnitudeT#

PlainQuantity’s magnitude expressed in particular units.

Parameters:

units (pint.PlainQuantity, str or dict) – destination units

property magnitude: MagnitudeT#

PlainQuantity’s magnitude. Long form for m

to(other: Quantity | str | dict[str, float | int | Decimal | Fraction] | UnitsContainer | Unit | None = None, *contexts, **ctx_kwargs) → PlainQuantity#

Return PlainQuantity rescaled to different units.

Parameters:

  • other (pint.PlainQuantity, str or dict) – destination units. (Default value = None)

  • *contexts (str or pint.Context) – Contexts to use in the transformation.

  • **ctx_kwargs – Values for the Context/s

Returns:

pint.PlainQuantity

to_base_units() → PlainQuantity[MagnitudeT]#

Return PlainQuantity rescaled to plain units.

to_compact(unit: UnitsContainer | None = None) → PlainQuantity#

“Return PlainQuantity rescaled to compact, human-readable units.

To get output in terms of a different unit, use the unit parameter.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (200e-9*ureg.s).to_compact()
<Quantity(200.0, 'nanosecond')>
>>> (1e-2*ureg('kg m/s^2')).to_compact('N')
<Quantity(10.0, 'millinewton')>
to_preferred(preferred_units: list[UnitLike] | None = None) → PlainQuantity#

Return Quantity converted to a unit composed of the preferred units.

Examples

>>> import pint
>>> ureg = pint.UnitRegistry()
>>> (1*ureg.acre).to_preferred([ureg.meters])
<Quantity(4046.87261, 'meter ** 2')>
>>> (1*(ureg.force_pound*ureg.m)).to_preferred([ureg.W])
<Quantity(4.44822162, 'watt * second')>
to_reduced_units() → PlainQuantity#

Return PlainQuantity scaled in place to reduced units, i.e. one unit per dimension. This will not reduce compound units (intentionally), nor can it make use of contexts at this time.

to_root_units() → PlainQuantity[MagnitudeT]#

Return PlainQuantity rescaled to root units.

property u: Unit#

PlainQuantity’s units. Short form for units

unit_items() → Iterable[tuple[str, float | int | Decimal | Fraction]]#

A view of the unit items.

property units: Unit#

PlainQuantity’s units. Long form for u

Exceptions and warnings#

exception pint.PintError[source]#

Base exception for all Pint errors.

exception pint.DefinitionSyntaxError(msg: str)[source]#

Raised when a textual definition has a syntax error.

exception pint.LogarithmicUnitCalculusError(units1: Any, units2: Any | None = None)[source]#

Raised on inappropriate operations with logarithmic units.

exception pint.DimensionalityError(units1: Any, units2: Any, dim1: str = '', dim2: str = '', extra_msg: str = '')[source]#

Raised when trying to convert between incompatible units.

exception pint.OffsetUnitCalculusError(units1: Any, units2: Any | None = None)[source]#

Raised on ambiguous operations with offset units.

exception pint.RedefinitionError(name: str, definition_type: type)[source]#

Raised when a unit or prefix is redefined.

exception pint.UndefinedUnitError(unit_names: str | Iterable[str])[source]#

Raised when the units are not defined in the unit registry.

exception pint.UnitStrippedWarning(msg: str)[source]#

Sharing registry among packages#

pint.get_application_registry()[source]#

Return the application registry. If set_application_registry() was never invoked, return a registry built using defaults_en.txt embedded in the pint package.

Returns:

pint.UnitRegistry

pint.set_application_registry(registry)[source]#

Set the application registry, which is used for unpickling operations and when invoking pint.Quantity or pint.Unit directly.

Parameters:

registry (pint.UnitRegistry)

Other functions#

pint.formatter(numerator: Iterable[tuple[str, Number]], denominator: Iterable[tuple[str, Number]], as_ratio: bool = True, single_denominator: bool = False, product_fmt: str = ' * ', division_fmt: str = ' / ', power_fmt: str = '{} ** {}', parentheses_fmt: str = '({0})', exp_call: FORMATTER = <built-in method format of str object>) → str[source]#

Format a list of (name, exponent) pairs.

Parameters:

  • items (list) – a list of (name, exponent) pairs.

  • as_ratio (bool, optional) – True to display as ratio, False as negative powers. (Default value = True)

  • single_denominator (bool, optional) – all with terms with negative exponents are collected together. (Default value = False)

  • product_fmt (str) – the format used for multiplication. (Default value = “ * “)

  • division_fmt (str) – the format used for division. (Default value = “ / “)

  • power_fmt (str) – the format used for exponentiation. (Default value = “{} ** {}”)

  • parentheses_fmt (str) – the format used for parenthesis. (Default value = “({0})”)

  • exp_call (callable()) – (Default value = lambda x: f”{x:n}”)

Returns:

str – the formula as a string.

pint.register_unit_format(name: str)[source]#

register a function as a new format for units

The registered function must have a signature of:

def new_format(unit, registry, **options):
    pass
Parameters:

name (str) – The name of the new format (to be used in the format mini-language). A error is raised if the new format would overwrite a existing format.

Examples

@pint.register_unit_format("custom")
def format_custom(unit, registry, **options):
    result = "<formatted unit>"  # do the formatting
    return result

ureg = pint.UnitRegistry()
u = ureg.m / ureg.s ** 2
f"{u:custom}"
pint.pi_theorem(quantities: dict[str, Any], registry: UnitRegistry | None = None)[source]#

Builds dimensionless quantities using the Buckingham π theorem

Parameters:

  • quantities (dict) – mapping between variable name and units

  • registry – (default value = None)

Returns:

type – a list of dimensionless quantities expressed as dicts

class pint.Context(name: str | None = None, aliases: tuple[str, ...] = (), defaults: dict[str, Any] | None = None)[source]#

A specialized container that defines transformation functions from one dimension to another. Each Dimension are specified using a UnitsContainer. Simple transformation are given with a function taking a single parameter.

Conversion functions may take optional keyword arguments and the context can have default values for these arguments.

Additionally, a context may host redefinitions.

A redefinition must be performed among units that already exist in the registry. It cannot change the dimensionality of a unit. The symbol and aliases are automatically inherited from the registry.

See ContextDefinition for the definition file syntax.

Parameters:

  • name (str or None, optional) – Name of the context (must be unique within the registry). Use None for anonymous Context. (Default value = None).

  • aliases (iterable of str) – Other names for the context.

  • defaults (None or dict) – Maps variable names to values.

Example

>>> from pint.util import UnitsContainer
>>> from pint import Context, UnitRegistry
>>> ureg = UnitRegistry()
>>> timedim = UnitsContainer({'[time]': 1})
>>> spacedim = UnitsContainer({'[length]': 1})
>>> def time_to_len(ureg, time):
...     'Time to length converter'
...     return 3. * time
>>> c = Context()
>>> c.add_transformation(timedim, spacedim, time_to_len)
>>> c.transform(timedim, spacedim, ureg, 2)
6.0
>>> def time_to_len_indexed(ureg, time, n=1):
...     'Time to length converter, n is the index of refraction of the material'
...     return 3. * time / n
>>> c = Context(defaults={'n':3})
>>> c.add_transformation(timedim, spacedim, time_to_len_indexed)
>>> c.transform(timedim, spacedim, ureg, 2)
2.0
>>> c.redefine("pound = 0.5 kg")
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