64 lines
1.4 KiB
Python
64 lines
1.4 KiB
Python
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# -*- coding: utf-8 -*-
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## Very simple unit support:
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## - creates variable names like 'mV' and 'kHz'
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## - the value assigned to the variable corresponds to the scale prefix
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## (mV = 0.001)
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## - the actual units are purely cosmetic for making code clearer:
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##
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## x = 20*pA is identical to x = 20*1e-12
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## No unicode variable names (μ,Ω) allowed until python 3
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SI_PREFIXES = 'yzafpnum kMGTPEZY'
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UNITS = 'm,s,g,W,J,V,A,F,T,Hz,Ohm,S,N,C,px,b,B'.split(',')
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allUnits = {}
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def addUnit(p, n):
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g = globals()
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v = 1000**n
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for u in UNITS:
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g[p+u] = v
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allUnits[p+u] = v
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for p in SI_PREFIXES:
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if p == ' ':
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p = ''
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n = 0
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elif p == 'u':
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n = -2
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else:
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n = SI_PREFIXES.index(p) - 8
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addUnit(p, n)
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cm = 0.01
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def evalUnits(unitStr):
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"""
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Evaluate a unit string into ([numerators,...], [denominators,...])
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Examples:
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N m/s^2 => ([N, m], [s, s])
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A*s / V => ([A, s], [V,])
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"""
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pass
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def formatUnits(units):
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"""
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Format a unit specification ([numerators,...], [denominators,...])
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into a string (this is the inverse of evalUnits)
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"""
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pass
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def simplify(units):
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"""
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Cancel units that appear in both numerator and denominator, then attempt to replace
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groups of units with single units where possible (ie, J/s => W)
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"""
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pass
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