sfepy.mechanics.units module

Some utilities for work with units of physical quantities.

class sfepy.mechanics.units.Quantity(name, unit_set)

A physical quantity in a given set of basic units.

Examples

Construct the stress quantity:

>>> from sfepy.mechanics.units import Unit, Quantity
>>> units = ['m', 's', 'kg', 'C']
>>> unit_set = [Unit(key) for key in units]
>>> q1 = Quantity('stress', unit_set)
>>> q1()
'1.0 Pa'

Show its unit using various prefixes:

>>> q1('m')
'1000.0 mPa'
>>> q1('')
'1.0 Pa'
>>> q1('k')
'0.001 kPa'
>>> q1('M')
'1e-06 MPa'

Construct the stress quantity in another unit set:

>>> units = ['mm', 's', 'kg', 'C']
>>> unit_set = [Unit(key) for key in units]
>>> q2 = Quantity('stress', unit_set)
>>> q2()
'1.0 kPa'

Show its unit using various prefixes:

>>> q2('m')
'1000000.0 mPa'
>>> q2('')
'1000.0 Pa'
>>> q2('k')
'1.0 kPa'
>>> q2('M')
'0.001 MPa'

class sfepy.mechanics.units.Unit(name)

A unit of a physical quantity. The prefix and coefficient of the unit are determined from to its name.

Examples

Construct some units:

>>> from sfepy.mechanics.units import Unit
>>> unit = Unit('mm')
>>> print unit
Unit:mm
  coef:
    0.001
  name:
    mm
  prefix:
    m
  prefix_length:
    1
  unit:
    m
>>> unit = Unit('kg')
>>> print unit
Unit:kg
  coef:
    1000.0
  name:
    kg
  prefix:
    k
  prefix_length:
    1
  unit:
    g

Get prefixes for a coefficient:

>>> Unit.get_prefix(100.0)
('d', 10.0)
>>> Unit.get_prefix(100.0, omit=('d',))
('k', 0.10000000000000001)

static get_prefix(coef, bias=0.1, omit=None)

Get the prefix and numerical multiplier corresponding to a numerical coefficient, omitting prefixes in omit tuple.

sfepy.mechanics.units.apply_unit_multipliers(values, unit_kinds, unit_multipliers)

Apply time, length and mass unit multipliers to given values with units corresponding to unit kinds.

Returns:

new_valueslist

The new values with applied unit multipliers

sfepy.mechanics.units.apply_units_to_pars(pars, pars_kinds, unit_multipliers)

Apply units in unit_multipliers to pars according to their kinds.

Parameters:

parsdict

The input parameters given as name : value items.

pars_kindsdict

The kinds of the parameters given as name : kind items, with kinds defined in apply_unit_multipliers().

unit_multiplierstuple

The time, length and mass unit multipliers.

Returns:

new_parsdict

The output parameters.

sfepy.mechanics.units.get_consistent_unit_set(length=None, time=None, mass=None, temperature=None)

Given a set of basic units, return a consistent set of derived units for quantities listed in the units_of_quantities dictionary.