/[escript]/trunk/escript/py_src/unitsSI.py
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1 gross 2398
2     ########################################################
3     #
4 jfenwick 2548 # Copyright (c) 2003-2009 by University of Queensland
5 gross 2398 # Earth Systems Science Computational Center (ESSCC)
6     # http://www.uq.edu.au/esscc
7     #
8     # Primary Business: Queensland, Australia
9     # Licensed under the Open Software License version 3.0
10     # http://www.opensource.org/licenses/osl-3.0.php
11     #
12     ########################################################
13    
14 jfenwick 2549 __copyright__="""Copyright (c) 2003-2009 by University of Queensland
15 gross 2398 Earth Systems Science Computational Center (ESSCC)
16     http://www.uq.edu.au/esscc
17     Primary Business: Queensland, Australia"""
18     __license__="""Licensed under the Open Software License version 3.0
19     http://www.opensource.org/licenses/osl-3.0.php"""
20     __url__="https://launchpad.net/escript-finley"
21     __author__="Lutz Gross, l.gross@uq.edu.au"
22    
23     ## @file unitsSI.py
24    
25     """
26 gross 2403 some tools supporting physical units and conversion
27 gross 2398
28     @var __author__: name of author
29     @var __copyright__: copyrights
30     @var __license__: licence agreement
31     @var __url__: url entry point on documentation
32     @var __version__: version
33     @var __date__: date of the version
34    
35     @var Yotta : prefix yotta, symbol: Y
36     @var Zetta : prefix zetta, symbol: Z
37     @var Exa : prefix exa, symbol: E
38     @var Peta : prefix peta, symbol: P
39     @var Tera : prefix tera, symbol: T
40     @var Giga : prefix giga, symbol: G
41     @var Mega : prefix mega, symbol: M
42     @var Kilo : prefix kilo, symbol: k
43     @var Hecto : prefix hecto, symbol: h
44     @var Deca : prefix deca, symbol: da
45     @var Deci : prefix deci, symbol: d
46     @var Centi : prefix centi, symbol: c
47     @var Milli : prefix milli, symbol: m
48     @var Micro : prefix micro, symbol: mu
49     @var Nano : prefix nano, symbol: n
50     @var Pico : prefix pico, symbol: p
51     @var Femto : prefix femto, symbol: f
52     @var Atto : prefix atto, symbol: a
53     @var Zepto : prefix zepto, symbol: z
54     @var Yocto : prefix yocto, symbol: y
55    
56     @var km : unit of kilo meter
57     @var m : unit of meter
58     @var cm : unit of centi meter
59     @var mm : unit of milli meter
60     @var sec: unit of second
61     @var minute : unit of minute
62     @var h : unit of hour
63     @var day : unit of day
64     @var yr : unit of year
65     @var Myr : unit of mega year
66     @var Gyr : unit of giga year
67     @var gram : unit of gram
68     @var kg : unit of kilo gram
69     @var lb : unit of pound
70     @var ton : metric ton
71     @var A : unit of Ampere
72 gross 2403 @var Hz: unit of Hertz (frequenacy)
73 gross 2398 @var N: unit of Newton (force)
74     @var Pa: unit of Pascal (pressure, stress)
75     @var atm: unit of atmosphere (pressure)
76     @var J: unit of Joule (energy, work)
77     @var W: unit of Watt (power)
78     @var C: unit of Coulomb (electric charge)
79     @var V: unit of Volt (electric potential)
80 gross 2403 @var F: unit of Farad (capacitance)
81 gross 2398 @var Ohm: unit of Ohm (electric resistance)
82 gross 2403 @var K : unit of Kelvin (temperature)
83 gross 2499 @var Mol : unit of Mole (temperature)
84 gross 2403 @var Celsius: unit of Celsius (temperature)
85     @var Fahrenheit : unit of Fahrenheit (temperature)
86 gross 2499 @var Poise : unit of Poise (dynamic viscosity)
87 gross 2398 @var R_Earth_equator: Earth's equatorial radius
88     @var R_Earth_poles: Earth's polar radius
89     @var R_Earth: Earth's radius
90     @var v_light: speed of light
91 ahallam 2448 @var pi: value of pi accurate to 10 decimal places
92 gross 2398 """
93 gross 2399 class Unit(object):
94     """
95 gross 2403 a general class to define a physical unit and convert from this unit to an appropriate SI unit.
96    
97     L{Unit} object have a dual purpose: Firstly physical units can be combined through *,/ and ** to form new physical units or to add prefixes such as
98     Milli to m to form mm=Milli*m. Moreover, a given floating point number x (or any other arithmetic object) can be converted from the physical unit to
99     the SI system, eg. 10*mm to create the value for 10mm which is the float number 0.01 in the SI system. In addition, a value in the SI unit can be
100     converted back to the given unit, eg. to express 0.01m in physical units of mm use 0.01/mm which will return 10.
101 gross 2399 """
102     def __init__(self, name, longname,a ,b ):
103     """
104 gross 2403 initializes the physical unit
105 gross 2399
106 gross 2403 @param name: short name of the physical unit or prefix
107 gross 2399 @type name: C{str}
108 gross 2403 @param longname: long name of the physical unit or prefix
109 gross 2399 @type longname: C{str}
110     @param a: absolute value in transformation
111     @type a: C{float}
112     @param b: slop in translation
113     @type b: C{float}
114     """
115     self.setName(name)
116     self.setLongName(longname)
117     self.__a=a
118     self.__b=b
119    
120     def __str__(self):
121     return self.getName()
122    
123     def getName(self):
124     """
125 gross 2403 Returns the name of the physical unit
126 gross 2399
127 gross 2403 @return: name of the physical unit
128 gross 2399 @rtype: C{str}
129     """
130     return self.__name
131    
132     def setName(self, name):
133     """
134 gross 2403 Sets the name of the physical unit
135 gross 2399
136 gross 2403 @param name: new name of the physical unit
137 gross 2399 @type name: C{str}
138     """
139     self.__name=name
140    
141     def getLongName(self):
142     """
143 gross 2403 Returns the long name of the physical unit
144 gross 2399
145 gross 2403 @return: name of the physical unit
146 gross 2399 @rtype: C{str}
147     """
148     return self.__longname
149    
150     def setLongName(self, name):
151     """
152 gross 2403 Sets the long name of the physical unit
153 gross 2399
154 gross 2403 @param name: new long name of the physical unit
155 gross 2399 @type name: C{str}
156     """
157     self.__longname=name
158    
159     def __call__(self,x):
160     """
161 gross 2403 Converts a value x in the physical unit self to SI
162 gross 2399
163     @param x: value to convert
164     @type x: an arithmetic object
165     """
166     return self.__b*x+self.__a
167    
168     def __mul__(self,other):
169     """
170     Performs self*other operation for two L{Unit} objects
171    
172 gross 2403 @param other: an other physical unit
173 gross 2399 @type other: L{Unit}
174     @rtype: L{Unit} or C{NotImplemented}
175     """
176     if isinstance(other, Unit):
177     a=self(other(0.))
178     b=(self(other(1.))-a)
179 gross 2403 if isinstance(other, _PowUnit) or isinstance(self,_DivUnit) or isinstance(self, _PowUnit):
180     return _ProdUnit(self.getName()+" "+other.getName(),self.getLongName()+"*"+other.getLongName(),a ,b)
181 gross 2399 else:
182 gross 2403 return _ProdUnit(self.getName()+other.getName(),self.getLongName()+"*"+other.getLongName(),a ,b)
183 gross 2399 else:
184     return NotImplemented
185    
186     def __rmul__(self,other):
187     """
188     Performs other*self operation
189    
190 gross 2403 @param other: an other L{Unit} or an arithmetic object. if other is a arithmetic object such as C{float} other is assumed to be given in the
191     physical unit C{self} and is converted into the corresponding SI unit.
192     @type other: L{Unit} or
193     @rtype: L{Unit} of or an arithmetic object
194 gross 2399 """
195     if isinstance(other, Unit):
196     a=other(self(0.))
197     b=(other(self(1.))-a)
198 gross 2403 if isinstance(other, _PowUnit) or isinstance(self, _PowUnit) or isinstance(other, _DivUnit):
199     return _ProdUnit(other.getName()+" "+self.getName(),other.getLongName()+"*"+self.getLongName(),a ,b)
200 gross 2399 else:
201 gross 2403 return _ProdUnit(other.getName()+self.getName(),other.getLongName()+"*"+self.getLongName(),a ,b)
202 gross 2399 else:
203     return self(other)
204    
205     def __div__(self,other):
206     """
207     Performs self*other operation for two L{Unit} objects
208    
209 gross 2403 @param other: an other physical unit
210 gross 2399 @type other: L{Unit}
211     @rtype: L{Unit} or C{NotImplemented}
212     """
213     if isinstance(other, Unit):
214     if abs(self(0.))+abs(other(0.))>0:
215 gross 2403 raise ValueError,"Division of physical units requires 0 absolute values"
216     if isinstance(other, (_ProdUnit, _DivUnit)):
217 gross 2399 # X/(c*d) or X/(c/d) requires brackets:
218 gross 2403 return _DivUnit(self.getName()+"/("+other.getName()+")",self.getLongName()+"/("+other.getLongName()+")",0 , self(1.)/other(1.))
219 gross 2399 else:
220 gross 2403 return _DivUnit(self.getName()+"/"+other.getName(),self.getLongName()+"/"+other.getLongName(),0 , self(1.)/other(1.))
221 gross 2399 else:
222     return NotImplemented
223     def __rdiv__(self,other):
224     """
225     Performs other/self operation
226    
227     @param other: an other L{Unit} or an arithmetic object
228     @type other: L{Unit} or an arithmetic object
229     @rtype: L{Unit} or an arithmetic object
230     """
231     if isinstance(other, Unit):
232     if abs(self(0.))+abs(other(0.))>0:
233 gross 2403 raise ValueError,"Division of physical units requires 0 absolute values"
234     if isinstance(self, (_ProdUnit, _DivUnit)):
235 gross 2399 # X/(a*b) or X/(a/b) requires brackets:
236 gross 2403 return _DivUnit(other.getName()+"/("+self.getName()+")",other.getLongName()+"/("+self.getLongName()+")",0 , other(1.)/self(1.))
237 gross 2399 else:
238 gross 2403 return _DivUnit(other.getName()+"/"+self.getName(),other.getLongName()+"/"+self.getLongName(),0 , other(1.)/self(1.))
239 gross 2399 else:
240     return (other-self(0.))/(self(1.)-self(0.))
241     def __pow__(self,other):
242     """
243     Performs self**other operation
244    
245     @param other: an exponent
246     @type other: C{int} or C{float}
247     @rtype: L{Unit}
248     """
249     if isinstance(other, float) or isinstance(other, int):
250     if abs(self(0.))>0:
251 gross 2403 raise ValueError,"Power of physical unit requires 0 absolute values"
252     if isinstance(self, (_ProdUnit, _DivUnit, _PowUnit)):
253     return _PowUnit("("+self.getName()+")^%s"%other, "("+self.getLongName()+")^%s"%other, 0., self(1.)**other)
254 gross 2399 else:
255 gross 2403 return _PowUnit(self.getName()+"^%s"%other, self.getLongName()+"^%s"%other, 0., self(1.)**other)
256 gross 2399 else:
257     return NotImplemented
258    
259 gross 2403 class _ProdUnit(Unit):
260 gross 2399 pass
261 gross 2403 class _DivUnit(Unit):
262 gross 2399 pass
263 gross 2403 class _PowUnit(Unit):
264 gross 2399 pass
265 gross 2403
266 gross 2398 #
267     # prefixes:
268     #
269 gross 2403 Yotta=Unit("Y","Yotta",0.,1.e24)
270     Zetta=Unit("Z","Zetta",0.,1.e21)
271     Exa=Unit("E","Exa",0.,1.e18)
272     Peta=Unit("P","Peta",0.,1.e15)
273     Tera=Unit("T","Tera",0.,1.e12)
274     Giga=Unit("G","Giga",0.,1.e9)
275     Mega=Unit("M","Mega",0.,1.e6)
276     Kilo=Unit("k","Kilo",0.,1.e3)
277     Hecto=Unit("h","Hecto",0.,1.e2)
278     Deca=Unit("da","Deca",0.,1.e1)
279     one=Unit("1","1",0.,1.)
280     Deci=Unit("d","Deci",0.,1.e-1)
281     Centi=Unit("c","Centi",0.,1.e-2)
282     Milli=Unit("m","Milli",0.,1.e-3)
283     Micro=Unit("mu","Micro",0.,1.e-6)
284     Nano=Unit("n","Nano",0.,1.e-9)
285     Pico=Unit("p","Pico",0.,1.e-12)
286     Femto=Unit("f","Femto",0.,1.e-15)
287     Atto=Unit("a","Atto",0.,1.e-18)
288     Zepto=Unit("z","Zepto",0.,1.e-21)
289     Yocto=Unit("y","Yocto",0.,1.e-24)
290 gross 2398 #
291     # length
292     #
293 gross 2403 m=Unit("m","meter",0.,1.)
294 gross 2398 km=Kilo*m
295     cm=Centi*m
296     mm=Milli*m
297     #
298     # time
299     #
300 gross 2403 sec=Unit("sec","second",0.,1.)
301     minute=Unit("min","minute",0.,60.)
302     h=Unit("h","hour",0.,60.*60.)
303     day=Unit("d","day",0.,60.*60.*24.)
304     yr=Unit("yr","year",0.,60.*60.*24.*365.2425)
305 gross 2398 Myr=Mega*yr
306     Gyr=Giga*yr
307     #
308     # mass
309     #
310 gross 2403 kg=Unit("kg","kg",0.,1.)
311 gross 2398 gram=Milli*kg
312 gross 2403 lb=Unit("lb","pound",0.,0.45359237)
313 gross 2398 ton=Kilo*kg
314     #
315     # electric current
316     #
317 gross 2403 A=Unit("A","Ampere",0.,1.)
318 gross 2398 #
319 gross 2403 # Temperature
320     #
321     K=Unit("K","Kelvin",0.,1.)
322     Celsius=Unit("C","Celsius",273.15,1.)
323     Fahrenheit=Unit("F","Fahrenheit",459.67*5./9.,5./9.)
324     #
325 gross 2398 # others
326     #
327 gross 2499 Mol=Unit("mole","Mole",0.,1.)
328 gross 2403 Hz=one/sec
329     N = Unit("N","Newton",0.,1.)
330     Pa = Unit("Pa","Pascal",0.,1.)
331     atm= Unit("atm","atmosphere",0.,101325.024)
332     J = Unit("J","Joule",0.,1.)
333     W= Unit("W","Watt",0.,1.)
334     C=Unit("C","Coulomb",0.,1.)
335     V = Unit("V","Volt",0.,1.)
336     F = Unit("F","Farad",0.,1.)
337     Ohm=Unit("Ohm","Ohm",0.,1.)
338 gross 2398 #
339 gross 2499 # Derived
340     #
341     Poise= gram/cm/sec
342     #
343 gross 2398 # some constants
344     #
345     R_Earth_equator=6378.1370*km
346     R_Earth_poles=6356.7523*km
347     R_Earth=(R_Earth_equator+R_Earth_poles)/2
348     v_light=299792458.*m/sec

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