65 lines
1.6 KiB
Python
65 lines
1.6 KiB
Python
# -*- 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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#
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# No unicode variable names (μ,Ω) allowed until python 3, but just assigning
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# them to the globals dict doesn't error in python 2.
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import unicodedata
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# All unicode identifiers get normalized automatically
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SI_PREFIXES = unicodedata.normalize("NFKC", u"yzafpnµm kMGTPEZY")
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UNITS = unicodedata.normalize("NFKC", u"m,s,g,W,J,V,A,F,T,Hz,Ohm,Ω,S,N,C,px,b,B,Pa").split(",")
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allUnits = {}
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def addUnit(prefix, val):
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g = globals()
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for u in UNITS:
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g[prefix + u] = val
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allUnits[prefix + u] = val
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for pre in SI_PREFIXES:
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v = SI_PREFIXES.index(pre) - 8
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if pre == " ":
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pre = ""
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addUnit(pre, 1000 ** v)
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addUnit("c", 0.01)
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addUnit("d", 0.1)
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addUnit("da", 10)
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addUnit("h", 100)
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# py2 compatibility
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addUnit("u", 1e-6)
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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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