u"""
This module defines two constants:
.. data:: DEFAULT_UNIT
The default unit of a BOM row: ``-`` (each)
.. data:: UNITS
All valid units of a BOM row.
"""
from django.utils.translation import ugettext_lazy as _
DEFAULT_UNIT = "-"
UNITS = (
(_(u'Amounts'), (
(DEFAULT_UNIT, _(u'Each')),
('mol', _(u'mol')),
)
),
(_(u'Lengths'), (
('mm', _(u'mm')),
('cm', _(u'cm')),
('dm', _(u'dm')),
('m', _(u'm')),
('km', _(u'km')),
)
),
(_(u'Volumes'), (
('m3', _(u'm\xb3')),
('mL', _(u'mL')),
('cL', _(u'cL')),
('dL', _(u'dL')),
('L', _(u'L')),
)
),
(_(u'Masses'), (
('mg', _(u'mg')),
('cg', _(u'cg')),
('dg', _(u'dg')),
('g', _(u'g')),
('kg', _(u'kg')),
)
),
)
[docs]class UnitConversionError(Exception):
"""
.. versionadded:: 1.1
Exception raised if an error occurs while converting
a value from one unit to another one.
"""
pass
FACTORS = {
'mm' : (0.001, 'm'),
'cm' : (0.01, 'm'),
'dm' : (0.1, 'm'),
'm' : (1., 'm'),
'km' : (1000, 'm'),
'mg' : (0.001, 'g'),
'cg' : (0.01, 'g'),
'dg' : (0.1, 'g'),
'g' : (1., 'g'),
'kg' : (1000, 'g'),
'mol' : (6.0221404e23, '-'),
'-' : (1., '-'),
'm3' : (1000., 'L'),
'mL' : (0.001, 'L'),
'cL' : (0.01, 'L'),
'dL' : (0.1, 'L'),
'L' : (1., 'L'),
}
[docs]def convert_unit(value, original_unit, new_unit):
"""
.. versionadded:: 1.1
Converts a value expressed in *original_unit* to
*new_unit*
:raises: :exc:`UnitConversionError` if the conversion is not possible.
Here is an example :
>>> convert_unit(1, 'm', 'mm')
1000.0
>>> convert_unit(5, 'dm', 'mm')
500.0
>>> convert_unit(5, 'dL', 'm3')
0.00050000000000000001
>>> convert_unit(5, 'dL', 'kg')
------------------------------------------------------------
Traceback (most recent call last):
File "<ipython console>", line 1, in <module>
File plmpapp/utils/units.py", line 80, in convert_unit
def convert_unit(value, original_unit, new_unit):
UnitConversionError: Inconsistent units (dL, kg)
"""
factor1, base1 = FACTORS[original_unit]
factor2, base2 = FACTORS[new_unit]
if base1 != base2:
raise UnitConversionError("Inconsistent units (%s, %s)" % (original_unit, new_unit))
return value * factor1 / factor2
