UnitBase¶

class
astropy.units.
UnitBase
[source]¶ Bases:
object
Abstract base class for units.
Most of the arithmetic operations on units are defined in this base class.
Should not be instantiated by users directly.
Attributes Summary
Returns the alias (long) names for this unit.
Return the bases of the unit.
Returns a copy of the current
Unit
instance with CGS units.Returns the canonical (short) name associated with this unit.
Returns all of the names associated with this unit.
Return the physical type on the unit.
Return the powers of the unit.
Return the scale of the unit.
Returns a copy of the current
Unit
instance in SI units.Methods Summary
compose
([equivalencies, units, max_depth, …])Return the simplest possible composite unit(s) that represent the given unit.
decompose
([bases])Return a unit object composed of only irreducible units.
find_equivalent_units
([equivalencies, …])Return a list of all the units that are the same type as
self
.in_units
(other[, value, equivalencies])Alias for
to
for backward compatibility with pynbody.is_equivalent
(other[, equivalencies])Returns
True
if this unit is equivalent toother
.is_unity
()Returns
True
if the unit is unscaled and dimensionless.to
(other[, value, equivalencies])Return the converted values in the specified unit.
to_string
([format])Output the unit in the given format as a string.
to_system
(system)Converts this unit into ones belonging to the given system.
Attributes Documentation

aliases
¶ Returns the alias (long) names for this unit.

bases
¶ Return the bases of the unit.

name
¶ Returns the canonical (short) name associated with this unit.

names
¶ Returns all of the names associated with this unit.

physical_type
¶ Return the physical type on the unit.
Examples
>>> from astropy import units as u >>> print(u.m.physical_type) length

powers
¶ Return the powers of the unit.

scale
¶ Return the scale of the unit.
Methods Documentation

compose
(equivalencies=[], units=None, max_depth=2, include_prefix_units=None)[source]¶ Return the simplest possible composite unit(s) that represent the given unit. Since there may be multiple equally simple compositions of the unit, a list of units is always returned.
 Parameters
 equivalencieslist of equivalence pairs, optional
A list of equivalence pairs to also list. See Equivalencies. This list is in addition to possible global defaults set by, e.g.,
set_enabled_equivalencies
. UseNone
to turn off all equivalencies. unitsset of units to compose to, optional
If not provided, any known units may be used to compose into. Otherwise,
units
is a dict, module or sequence containing the units to compose into. max_depthint, optional
The maximum recursion depth to use when composing into composite units.
 include_prefix_unitsbool, optional
When
True
, include prefixed units in the result. Default isTrue
if a sequence is passed in tounits
,False
otherwise.
 Returns
 unitslist of
CompositeUnit
A list of candidate compositions. These will all be equally simple, but it may not be possible to automatically determine which of the candidates are better.
 unitslist of

decompose
(bases={})[source]¶ Return a unit object composed of only irreducible units.
 Parameters
 basessequence of UnitBase, optional
The bases to decompose into. When not provided, decomposes down to any irreducible units. When provided, the decomposed result will only contain the given units. This will raises a
UnitsError
if it’s not possible to do so.
 Returns
 unitCompositeUnit object
New object containing only irreducible unit objects.

find_equivalent_units
(equivalencies=[], units=None, include_prefix_units=False)[source]¶ Return a list of all the units that are the same type as
self
. Parameters
 equivalencieslist of equivalence pairs, optional
A list of equivalence pairs to also list. See Equivalencies. Any list given, including an empty one, supersedes global defaults that may be in effect (as set by
set_enabled_equivalencies
) unitsset of units to search in, optional
If not provided, all defined units will be searched for equivalencies. Otherwise, may be a dict, module or sequence containing the units to search for equivalencies.
 include_prefix_unitsbool, optional
When
True
, include prefixed units in the result. Default isFalse
.
 Returns

in_units
(other, value=1.0, equivalencies=[])[source]¶ Alias for
to
for backward compatibility with pynbody.

is_equivalent
(other, equivalencies=[])[source]¶ Returns
True
if this unit is equivalent toother
. Parameters
 otherunit object or string or tuple
The unit to convert to. If a tuple of units is specified, this method returns true if the unit matches any of those in the tuple.
 equivalencieslist of equivalence pairs, optional
A list of equivalence pairs to try if the units are not directly convertible. See Equivalencies. This list is in addition to possible global defaults set by, e.g.,
set_enabled_equivalencies
. UseNone
to turn off all equivalencies.
 Returns
 bool

to
(other, value=1.0, equivalencies=[])[source]¶ Return the converted values in the specified unit.
 Parameters
 otherunit object or string
The unit to convert to.
 valuescalar int or float, or sequence convertible to array, optional
Value(s) in the current unit to be converted to the specified unit. If not provided, defaults to 1.0
 equivalencieslist of equivalence pairs, optional
A list of equivalence pairs to try if the units are not directly convertible. See Equivalencies. This list is in addition to possible global defaults set by, e.g.,
set_enabled_equivalencies
. UseNone
to turn off all equivalencies.
 Returns
 valuesscalar or array
Converted value(s). Input value sequences are returned as numpy arrays.
 Raises
 UnitsError
If units are inconsistent

to_string
(format=<class 'astropy.units.format.generic.Generic'>)[source]¶ Output the unit in the given format as a string.
 Parameters
 format
astropy.units.format.Base
instance or str The name of a format or a formatter object. If not provided, defaults to the generic format.
 format

to_system
(system)[source]¶ Converts this unit into ones belonging to the given system. Since more than one result may be possible, a list is always returned.
 Parameters
 systemmodule
The module that defines the unit system. Commonly used ones include
astropy.units.si
andastropy.units.cgs
.To use your own module it must contain unit objects and a sequence member named
bases
containing the base units of the system.
 Returns
 unitslist of
CompositeUnit
The list is ranked so that units containing only the base units of that system will appear first.
 unitslist of
