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ipython_physics.py
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ipython_physics.py
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# -*- coding: utf-8 -*-
"""
IPython 5+ extension for physical quantity input.
See README.txt for usage examples.
Author: Georg Brandl <[email protected]>.
This file has been placed in the public domain.
"""
__version__ = "0.1.0"
import re
import sys
from math import pi
from functools import reduce, total_ordering
import numpy as np
# note: deprecated since IPython 7
from IPython.core.inputtransformer import InputTransformer
# allow uncertain values if the "uncertainties" package is available
try:
from uncertainties import ufloat, Variable, AffineScalarFunc
import uncertainties.umath as unp
uncertain = (Variable, AffineScalarFunc)
def valuetype(val_unit):
v, u = val_unit
if isinstance(v, uncertain):
return v
return ufloat((v, u))
except ImportError:
uncertain = ()
unp = np
def valuetype(val_unit):
return val_unit[0]
class UnitError(ValueError):
pass
# Adapted from ScientificPython:
# Written by Konrad Hinsen <[email protected]>
# with contributions from Greg Ward
# last revision: 2007-5-25
class NumberDict(dict):
"""Dictionary storing numerical values.
An instance of this class acts like an array of number with generalized
(non-integer) indices. A value of zero is assumed for undefined
entries. NumberDict instances support addition, and subtraction with other
NumberDict instances, and multiplication and division by scalars.
"""
def __getitem__(self, item):
try:
return dict.__getitem__(self, item)
except KeyError:
return 0
def __add__(self, other):
sum_dict = NumberDict()
for key in self:
sum_dict[key] = self[key]
for key in other:
sum_dict[key] = sum_dict[key] + other[key]
return sum_dict
def __radd__(self, other):
return NumberDict(other) + self
def __sub__(self, other):
sum_dict = NumberDict()
for key in self:
sum_dict[key] = self[key]
for key in other:
sum_dict[key] = sum_dict[key] - other[key]
return sum_dict
def __rsub__(self, other):
return NumberDict(other) - self
def __mul__(self, other):
new = NumberDict()
for key in self:
new[key] = other*self[key]
return new
__rmul__ = __mul__
def __truediv__(self, other):
new = NumberDict()
for key in self:
new[key] = self[key]/other
return new
# Type checks
def isPhysicalUnit(x):
return hasattr(x, 'factor') and hasattr(x, 'powers')
def isPhysicalQuantity(x):
return hasattr(x, 'value') and hasattr(x, 'unit')
@total_ordering
class PhysicalUnit(object):
"""Physical unit.
A physical unit is defined by a name (possibly composite), a scaling factor,
and the exponentials of each of the SI base units that enter into it. Units
can be multiplied, divided, and raised to integer powers.
"""
def __init__(self, names, factor, powers, offset=0):
"""
@param names: a dictionary mapping each name component to its
associated integer power (e.g. C{{'m': 1, 's': -1}})
for M{m/s}). As a shorthand, a string may be passed
which is assigned an implicit power 1.
@param factor: a scaling factor
@param powers: the integer powers for each of the nine base units
@param offset: an additive offset to the base unit (used only for
temperatures)
"""
if isinstance(names, str):
self.names = NumberDict()
self.names[names] = 1
else:
self.names = names
self.factor = factor
self.offset = offset
self.powers = powers
def set_name(self, name):
self.names = NumberDict()
self.names[name] = 1
def name(self):
num = ''
denom = ''
for unit in self.names:
power = self.names[unit]
if power < 0:
denom = denom + '/' + unit
if power < -1:
denom = denom + '**' + str(-power)
elif power > 0:
num = num + '*' + unit
if power > 1:
num = num + '**' + str(power)
if len(num) == 0:
num = '1'
if denom == '':
return ''
else:
num = num[1:]
return num + denom
@property
def is_dimensionless(self):
return not reduce(lambda a, b: a or b, self.powers)
@property
def is_angle(self):
return self.powers[7] == 1 and \
reduce(lambda a, b: a + b, self.powers) == 1
def __str__(self):
return self.name()
def __repr__(self):
return '<PhysicalUnit ' + self.name() + '>'
def __eq__(self, other):
if self.powers != other.powers:
raise UnitError('Incompatible units')
return self.factor == other.factor
def __lt__(self, other):
if self.powers != other.powers:
raise UnitError('Incompatible units')
return self.factor < other.factor
def __mul__(self, other):
if self.offset != 0 or (isPhysicalUnit(other) and other.offset != 0):
raise UnitError('Cannot multiply units with non-zero offset')
if isPhysicalUnit(other):
return PhysicalUnit(self.names + other.names,
self.factor * other.factor,
[a+b for (a,b) in zip(self.powers, other.powers)])
else:
return PhysicalUnit(self.names + {str(other): 1},
self.factor * other, self.powers,
self.offset * other)
__rmul__ = __mul__
def __truediv__(self, other):
if self.offset != 0 or (isPhysicalUnit(other) and other.offset != 0):
raise UnitError('Cannot divide units with non-zero offset')
if isPhysicalUnit(other):
return PhysicalUnit(self.names - other.names,
self.factor / other.factor,
[a-b for (a,b) in zip(self.powers, other.powers)])
else:
return PhysicalUnit(self.names+{str(other): -1},
self.factor/other, self.powers)
def __rtruediv__(self, other):
if self.offset != 0 or (isPhysicalUnit(other) and other.offset != 0):
raise UnitError('Cannot divide units with non-zero offset')
if isPhysicalUnit(other):
return PhysicalUnit(other.names - self.names,
other.factor/self.factor,
[a-b for (a,b) in zip(other.powers, self.powers)])
else:
return PhysicalUnit({str(other): 1} - self.names,
other / self.factor,
[-x for x in self.powers])
def __pow__(self, other):
if self.offset != 0:
raise UnitError('Cannot exponentiate units with non-zero offset')
if isinstance(other, int):
return PhysicalUnit(other*self.names, pow(self.factor, other),
[x*other for x in self.powers])
if isinstance(other, float):
inv_exp = 1./other
rounded = int(np.floor(inv_exp + 0.5))
if abs(inv_exp-rounded) < 1.e-10:
if reduce(lambda a, b: a and b,
map(lambda x, e=rounded: x%e == 0, self.powers)):
f = pow(self.factor, other)
p = [x/rounded for x in self.powers]
if reduce(lambda a, b: a and b,
map(lambda x, e=rounded: x%e == 0,
self.names.values())):
names = self.names/rounded
else:
names = NumberDict()
if f != 1.:
names[str(f)] = 1
for i in range(len(p)):
names[_base_names[i]] = p[i]
return PhysicalUnit(names, f, p)
else:
raise UnitError('Illegal exponent %f' % other)
raise UnitError('Only integer and inverse integer exponents allowed')
def conversion_factor_to(self, other):
"""Return conversion factor to another unit."""
if self.powers != other.powers:
raise UnitError('Incompatible units')
if self.offset != other.offset and self.factor != other.factor:
raise UnitError(('Unit conversion (%s to %s) cannot be expressed ' +
'as a simple multiplicative factor') %
(self.name(), other.name()))
return self.factor/other.factor
def conversion_tuple_to(self, other):
"""Return conversion factor and offset to another unit."""
if self.powers != other.powers:
raise UnitError('Incompatible units')
# let (s1,d1) be the conversion tuple from 'self' to base units
# (ie. (x+d1)*s1 converts a value x from 'self' to base units,
# and (x/s1)-d1 converts x from base to 'self' units)
# and (s2,d2) be the conversion tuple from 'other' to base units
# then we want to compute the conversion tuple (S,D) from
# 'self' to 'other' such that (x+D)*S converts x from 'self'
# units to 'other' units
# the formula to convert x from 'self' to 'other' units via the
# base units is (by definition of the conversion tuples):
# ( ((x+d1)*s1) / s2 ) - d2
# = ( (x+d1) * s1/s2) - d2
# = ( (x+d1) * s1/s2 ) - (d2*s2/s1) * s1/s2
# = ( (x+d1) - (d1*s2/s1) ) * s1/s2
# = (x + d1 - d2*s2/s1) * s1/s2
# thus, D = d1 - d2*s2/s1 and S = s1/s2
factor = self.factor / other.factor
offset = self.offset - (other.offset * other.factor / self.factor)
return (factor, offset)
# Helper functions
def _findUnit(unit):
if isinstance(unit, str):
name = unit.strip().replace('^', '**').replace('µ', 'mu').replace('°', 'deg')
try:
unit = eval(name, _unit_table)
except NameError:
raise UnitError('Invalid or unknown unit in %r' % unit)
for cruft in ['__builtins__', '__args__']:
try: del _unit_table[cruft]
except: pass
if not isPhysicalUnit(unit):
raise UnitError(str(unit) + ' is not a unit')
return unit
def _convertValue(value, src_unit, target_unit):
(factor, offset) = src_unit.conversion_tuple_to(target_unit)
return (value + offset) * factor
@total_ordering
class PhysicalQuantity(object):
"""Physical quantity with units.
PhysicalQuantity instances allow addition, subtraction, multiplication, and
division with each other as well as multiplication, division, and
exponentiation with numbers. Addition and subtraction check that the units
of the two operands are compatible and return the result in the units of the
first operand. A limited set of mathematical functions (from numpy) is
applicable as well.
"""
global_precision = 8
_number = re.compile(r'([+-]?[0-9]+(?:\.[0-9]*)?(?:[eE][+-]?[0-9]+)?)'
r'(?:\s+\+\/-\s+([+-]?[0-9]+(?:\.[0-9]*)?(?:[eE][+-]?[0-9]+)?))?')
def __init__(self, value, unit=None, stdev=None):
"""There are two constructor calling patterns:
1. PhysicalQuantity(value, unit), where value is any number and unit is
a string defining the unit
2. PhysicalQuantity(value_with_unit), where value_with_unit is a string
that contains both the value and the unit, i.e. '1.5 m/s'. This form
is provided for more convenient interactive use.
"""
if unit is not None:
self.value = valuetype((value, stdev or 0))
self.unit = _findUnit(unit)
else:
s = value.strip()
match = self._number.match(s)
if match is None:
raise UnitError('No number found in %r' % value)
self.value = valuetype((float(match.group(1)),
float(match.group(2) or 0)))
self.unit = _findUnit(s[match.end(0):])
def __str__(self):
prec = self.global_precision
unit = self.unit.name().replace('**', '^')
if isinstance(self.value, uncertain):
stdev = self.value.std_dev()
if stdev:
return '%.*g +/- %.*g %s' % (prec, self.value.nominal_value,
prec, stdev, unit)
return '%.*g %s' % (prec, self.value.nominal_value, unit)
return '%.*g %s' % (prec, self.value, unit)
def __repr__(self):
return self.__str__()
def _sum(self, other, sign1, sign2):
if not isPhysicalQuantity(other):
raise UnitError('Incompatible types')
new_value = sign1 * self.value + \
sign2 * other.value * other.unit.conversion_factor_to(self.unit)
return self.__class__(new_value, self.unit)
def __add__(self, other):
return self._sum(other, 1, 1)
__radd__ = __add__
def __sub__(self, other):
return self._sum(other, 1, -1)
def __rsub__(self, other):
return self._sum(other, -1, 1)
def __eq__(self, other):
diff = self._sum(other, 1, -1)
return diff.value == 0
def __lt__(self, other):
diff = self._sum(other, 1, -1)
return diff.value < 0
def __mul__(self, other):
if not isPhysicalQuantity(other):
return self.__class__(self.value * other, self.unit)
value = self.value * other.value
unit = self.unit * other.unit
if unit.is_dimensionless:
return value * unit.factor
else:
return self.__class__(value, unit)
__rmul__ = __mul__
def __div__(self, other):
if not isPhysicalQuantity(other):
return self.__class__(self.value / other, self.unit)
value = self.value / other.value
unit = self.unit / other.unit
if unit.is_dimensionless:
return value * unit.factor
else:
return self.__class__(value, unit)
def __rdiv__(self, other):
if not isPhysicalQuantity(other):
return self.__class__(other / self.value, pow(self.unit, -1))
value = other.value / self.value
unit = other.unit / self.unit
if unit.is_dimensionless:
return value * unit.factor
else:
return self.__class__(value, unit)
__truediv__ = __div__
__rtruediv__ = __rdiv__
def __pow__(self, other):
if isPhysicalQuantity(other):
raise UnitError('Exponents must be dimensionless')
return self.__class__(pow(self.value, other), pow(self.unit, other))
def __rpow__(self, other):
raise UnitError('Exponents must be dimensionless')
def __abs__(self):
return self.__class__(abs(self.value), self.unit)
def __pos__(self):
return self
def __neg__(self):
return self.__class__(-self.value, self.unit)
def __nonzero__(self):
return self.value != 0
def __format__(self, *args, **kw):
return "{1:{0}} {2}".format(args[0],self.value, self.unit)
def convert(self, unit):
"""Change the unit and adjust the value such that the combination is
equivalent to the original one. The new unit must be compatible with the
previous unit of the object.
"""
unit = _findUnit(unit)
self.value = _convertValue(self.value, self.unit, unit)
self.unit = unit
def _round(self, x):
if np.greater(x, 0.):
return np.floor(x)
else:
return np.ceil(x)
def to(self, *units):
"""Express the quantity in different units. If one unit is specified, a
new PhysicalQuantity object is returned that expresses the quantity in
that unit. If several units are specified, the return value is a tuple
of PhysicalObject instances with with one element per unit such that the
sum of all quantities in the tuple equals the the original quantity and
all the values except for the last one are integers. This is used to
convert to irregular unit systems like hour/minute/second.
"""
units = [_findUnit(x) for x in units]
if len(units) == 1:
unit = units[0]
value = _convertValue(self.value, self.unit, unit)
return self.__class__(value, unit)
else:
units.sort()
result = []
value = self.value
unit = self.unit
for i in range(len(units)-1,-1,-1):
value = value*unit.conversion_factor_to(units[i])
if i == 0:
rounded = value
else:
rounded = self._round(value)
result.append(self.__class__(rounded, units[i]))
value = value - rounded
unit = units[i]
return tuple(result)
@staticmethod
def any_to(qty, unit):
if not isPhysicalQuantity(qty):
qty = PhysicalQuantity(qty, 'rad')
return qty.to(unit)
@property
def base(self):
"""Returns the same quantity converted to base units."""
new_value = self.value * self.unit.factor
num = ''
denom = ''
for i in range(9):
unit = _base_names[i]
power = self.unit.powers[i]
if power < 0:
denom += '/' + unit
if power < -1:
denom += '**' + str(-power)
elif power > 0:
num += '*' + unit
if power > 1:
num += '**' + str(power)
if len(num) == 0:
num = '1'
if denom == '':
return new_value
else:
num = num[1:]
return self.__class__(new_value, num + denom)
@property
def cgs(self):
"""Returns the same quantity converted to cgs units."""
new_value = self.value * self.unit.factor
num = ''
denom = ''
for i in range(9):
unit_name = _base_names[i]
cgs_name = _cgs_names[i]
power = self.unit.powers[i]
conversion_factor = Q('1 '+unit_name).to(cgs_name).value
new_value *= conversion_factor**power
if power < 0:
denom += '/' + cgs_name
if power < -1:
denom += '**' + str(-power)
elif power > 0:
num += '*' + cgs_name
if power > 1:
num += '**' + str(power)
if len(num) == 0:
num = '1'
if denom == '':
return new_value
else:
num = num[1:]
return self.__class__(new_value, num + denom)
# implementations of special functions, used by numpy ufuncs
def sqrt(self):
return pow(self, 0.5)
def sin(self):
if self.unit.is_angle:
return unp.sin(self.value *
self.unit.conversion_factor_to(_unit_table['rad']))
else:
raise UnitError('Argument of sin must be an angle')
def cos(self):
if self.unit.is_angle:
return unp.cos(self.value *
self.unit.conversion_factor_to(_unit_table['rad']))
else:
raise UnitError('Argument of cos must be an angle')
def tan(self):
if self.unit.is_angle:
return unp.tan(self.value *
self.unit.conversion_factor_to(_unit_table['rad']))
else:
raise UnitError('Argument of tan must be an angle')
Q = PhysicalQuantity
# SI unit definitions
_base_names = ['m', 'kg', 's', 'A', 'K', 'mol', 'cd', 'rad', 'sr']
_base_units = [
('m', PhysicalUnit('m', 1., [1,0,0,0,0,0,0,0,0])),
('g', PhysicalUnit('g', 0.001, [0,1,0,0,0,0,0,0,0])),
('s', PhysicalUnit('s', 1., [0,0,1,0,0,0,0,0,0])),
('A', PhysicalUnit('A', 1., [0,0,0,1,0,0,0,0,0])),
('K', PhysicalUnit('K', 1., [0,0,0,0,1,0,0,0,0])),
('mol', PhysicalUnit('mol', 1., [0,0,0,0,0,1,0,0,0])),
('cd', PhysicalUnit('cd', 1., [0,0,0,0,0,0,1,0,0])),
('rad', PhysicalUnit('rad', 1., [0,0,0,0,0,0,0,1,0])),
('sr', PhysicalUnit('sr', 1., [0,0,0,0,0,0,0,0,1])),
]
_cgs_names = ['cm', 'g', 's', 'abA', 'K', 'mol', 'cd', 'rad', 'sr']
_prefixes = [
('Y', 1.e24), ('Z', 1.e21), ('E', 1.e18), ('P', 1.e15), ('T', 1.e12),
('G', 1.e9), ('M', 1.e6), ('k', 1.e3), ('h', 1.e2), ('da', 1.e1),
('d', 1.e-1), ('c', 1.e-2), ('m', 1.e-3), ('mu', 1.e-6), ('n', 1.e-9),
('p', 1.e-12), ('f', 1.e-15), ('a', 1.e-18), ('z', 1.e-21),
('y', 1.e-24),
]
_unit_table = {}
for unit in _base_units:
_unit_table[unit[0]] = unit[1]
def _addUnit(name, unit, comment=''):
if name in _unit_table:
raise KeyError('Unit ' + name + ' already defined')
if type(unit) == type(''):
unit = eval(unit, _unit_table)
for cruft in ['__builtins__', '__args__']:
try: del _unit_table[cruft]
except: pass
unit.set_name(name)
_unit_table[name] = unit
def _addPrefixed(unit):
_prefixed_names = []
for prefix in _prefixes:
name = prefix[0] + unit
_addUnit(name, prefix[1]*_unit_table[unit])
_prefixed_names.append(name)
# SI derived units; these automatically get prefixes
_unit_table['kg'] = PhysicalUnit('kg', 1., [0,1,0,0,0,0,0,0,0])
_addUnit('Hz', '1/s', 'Hertz')
_addUnit('N', 'm*kg/s**2', 'Newton')
_addUnit('Pa', 'N/m**2', 'Pascal')
_addUnit('J', 'N*m', 'Joule')
_addUnit('W', 'J/s', 'Watt')
_addUnit('C', 's*A', 'Coulomb')
_addUnit('V', 'W/A', 'Volt')
_addUnit('F', 'C/V', 'Farad')
_addUnit('ohm', 'V/A', 'Ohm')
_addUnit('S', 'A/V', 'Siemens')
_addUnit('Wb', 'V*s', 'Weber')
_addUnit('T', 'Wb/m**2', 'Tesla')
_addUnit('H', 'Wb/A', 'Henry')
_addUnit('lm', 'cd*sr', 'Lumen')
_addUnit('lx', 'lm/m**2', 'Lux')
_addUnit('Bq', '1/s', 'Becquerel')
_addUnit('Gy', 'J/kg', 'Gray')
_addUnit('Sv', 'J/kg', 'Sievert')
_addUnit('kat', 'mol/s', 'Katal')
_addUnit('abA', '10*A', 'Abampere')
del _unit_table['kg']
for unit in list(_unit_table):
_addPrefixed(unit)
# Fundamental constants, as far as needed to define other units
_unit_table['pi'] = np.pi
_addUnit('c0', '299792458.*m/s', 'speed of light')
_addUnit('mu0', '4.e-7*pi*N/A**2', 'permeability of vacuum')
_addUnit('eps0', '1/mu0/c0**2', 'permittivity of vacuum')
_addUnit('hplanck', '6.62606957e-34*J*s', 'Planck constant')
_addUnit('hbar', 'hplanck/(2*pi)', 'Planck constant / 2pi')
_addUnit('e0', '1.602176565e-19*C', 'elementary charge')
_addUnit('me', '9.10938291e-31*kg', 'electron mass')
_addUnit('kb', '1.3806488e-23*J/K', 'Boltzmann constant')
# Time units
_addUnit('min', '60*s', 'minute')
_addUnit('h', '60*min', 'hour')
_addUnit('d', '24*h', 'day')
_addUnit('wk', '7*d', 'week')
_addUnit('yr', '365.25*d', 'year')
_addPrefixed('yr')
_addUnit('fortnight', '1209600*s', '14 days')
# Length units
_addUnit('inch', '2.54*cm', 'inch')
_addUnit('ft', '12*inch', 'foot')
_addUnit('yd', '3*ft', 'yard')
_addUnit('mi', '5280.*ft', '(British) mile')
_addUnit('nmi', '1852.*m', 'Nautical mile')
_addUnit('Ang', '1.e-10*m', 'Angstrom')
_addUnit('AA', '1.e-10*m', 'Angstrom')
_addUnit('lyr', 'c0*yr', 'light year')
_addUnit('Bohr', '4*pi*eps0*hbar**2/me/e0**2', 'Bohr radius')
_addUnit('furlong', '201.168*m', 'furlongs')
_addUnit('au', '149597870691*m', 'astronomical unit')
# Area units
_addUnit('ha', '10000*m**2', 'hectare')
_addUnit('acres', 'mi**2/640', 'acre')
_addUnit('b', '1.e-28*m', 'barn')
# Volume units
_addUnit('l', 'dm**3', 'liter')
_addUnit('dl', '0.1*l', 'deci liter')
_addUnit('cl', '0.01*l', 'centi liter')
_addUnit('ml', '0.001*l', 'milli liter')
_addUnit('mul', '0.000001*l', 'micro liter')
_addUnit('tsp', '4.92892159375*ml', 'teaspoon')
_addUnit('tbsp', '3*tsp', 'tablespoon')
_addUnit('floz', '2*tbsp', 'fluid ounce')
_addUnit('cup', '8*floz', 'cup')
_addUnit('pt', '16*floz', 'pint')
_addUnit('qt', '2*pt', 'quart')
_addUnit('galUS', '4*qt', 'US gallon')
_addUnit('galUK', '4.54609*l', 'British gallon')
# Mass units
_addUnit('t', '1000*kg', 'Metric ton')
_addUnit('amu', '1.660538921e-27*kg', 'atomic mass units')
_addUnit('Da', '1*amu', 'Dalton')
_addUnit('oz', '28.349523125*g', 'ounce')
_addUnit('lb', '16*oz', 'pound')
_addUnit('ton', '2000*lb', 'US ton')
# Force units
_addUnit('dyn', '1.e-5*N', 'dyne (cgs unit)')
# Energy units
_addUnit('erg', '1.e-7*J', 'erg (cgs unit)')
_addUnit('eV', 'e0*V', 'electron volt')
_addUnit('Hartree', 'me*e0**4/16/pi**2/eps0**2/hbar**2', 'Wavenumbers/inverse cm')
_addUnit('Ken', 'kb*K', 'Kelvin as energy unit')
_addUnit('cal', '4.184*J', 'thermochemical calorie')
_addUnit('kcal', '1000*cal', 'thermochemical kilocalorie')
_addUnit('cali', '4.1868*J', 'international calorie')
_addUnit('kcali', '1000*cali', 'international kilocalorie')
_addUnit('Btu', '1055.05585262*J', 'British thermal unit')
_addUnit('tTNT', '4.184*(10**9)*J', 'ton TNT')
_addUnit('MtTNT', '4.184*(10**15)*J', 'Mega ton TNT')
_addPrefixed('eV')
# Electromagnetic units
_addUnit('G', '1e-4*T', 'Gauss')
_addUnit('Oe', '79.5774715*A/m', 'Oersted')
_addPrefixed('G')
_addPrefixed('Oe')
# Power units
_addUnit('hp', '745.7*W', 'horsepower')
# Pressure units
_addUnit('bar', '1.e5*Pa', 'bar (cgs unit)')
_addUnit('mbar', '1.e2*Pa', 'millibar')
_addUnit('kbar', '1.e8*Pa', 'kilobar')
_addUnit('atm', '101325.*Pa', 'standard atmosphere')
_addUnit('torr', 'atm/760', 'torr = mm of mercury')
_addUnit('psi', '6894.75729317*Pa', 'pounds per square inch')
# Angle units
_addUnit('deg', 'pi*rad/180', 'degrees')
_addUnit('arcmin', 'pi*rad/180/60', 'minutes of arc')
_addUnit('arcsec', 'pi*rad/180/3600', 'seconds of arc')
_unit_table['cycles'] = 2*np.pi
# Temperature units -- can't use the 'eval' trick that _addUnit provides
# for degC and degF because you can't add units
kelvin = _findUnit('K')
_addUnit('degR', '(5./9.)*K', 'degrees Rankine')
_addUnit('degC', PhysicalUnit(None, 1.0, kelvin.powers, 273.15),
'degrees Celcius')
_addUnit('degF', PhysicalUnit(None, 5./9., kelvin.powers, 459.67),
'degree Fahrenheit')
del kelvin
# Radiation-related units
_addUnit('Ci', '3.7e10*Bq', 'Curie')
_addUnit('rem', '0.01*Sv', 'Rem')
_addPrefixed('Ci')
_addPrefixed('rem')
# Astronomical units
_addUnit('Msol', '1.98892e30*kg', 'solar mass')
_addUnit('Lsol', '3.839e26*W', 'solar luminosity')
_addUnit('pc', '3.08568025e16*m')
_addPrefixed('pc')
# Important physical constants
_constants = [
('pi', np.pi),
('e', np.e),
('c0', Q('299792458. m/s')),
('mu0', Q('4.e-7 pi*N/A**2').base),
('eps0', Q('1 1/mu0/c0**2').base),
('Grav', Q('6.67384e-11 m**3/kg/s**2')),
('hpl', Q('6.62606957e-34 J*s')),
('hbar', Q('6.62606957e-34 J*s')/(2*pi)),
('e0', Q('1.602176565e-19 C')),
('me', Q('9.10938291e-31 kg')),
('mp', Q('1.672621777e-27 kg')),
('mn', Q('1.674927351e-27 kg')),
('NA', Q('6.02214129e23 1/mol')),
('kb', Q('1.3806488e-23 J/K')),
('g0', Q('9.80665 m/s**2')),
('R', Q('8.3144621 J/mol/K')),
('alpha', 7.2973525698e-3),
('Ry', Q('10973731.568539 1/m')),
('mu_n', Q('-0.96623647e-26 J/T')),
('gamma', Q('183.247179 MHz/T')),
('h0', 0.704), # WMAP-7 + BAO constraint
('sigmaT', Q('6.652453e-29 m**2')),
]
name = r'([_a-zA-Z]\w*)'
number = r'(-?[\d0-9.eE-]+)'
unit = r'([a-zA-Z1°µ][a-zA-Z0-9°µ/*^-]*)'
quantity = number + r'(?:\s+\+\/-\s+' + number + ')?' + r'\s+' + unit
inline_unit_re = re.compile(r'\((%s)\)' % quantity)
slash_conv_re = re.compile(r'^(.*?)//\s*%s$' % unit)
slash_last_re = re.compile(r'^()\(/, %s\)$' % unit)
trailing_conv_re = re.compile(r'\s*//\s*%s$' % unit)
nice_assign_re = re.compile(r'^%s\s*=\s*(%s)$' % (name, quantity))
quantity_re = re.compile(quantity)
subst_re = re.compile(r'\?' + name)
def replace_inline(match):
"""Replace an inline unit expression, e.g. ``(1 m)``, by valid Python code
using a Quantity call.
"""
return '(Quantity(\'' + match.group(1) + '\'))'
def replace_slash(match):
"""Replace a double-slash unit conversion, e.g. ``c // km/s``, by valid
Python code using a Quantity call.
"""
expr = match.group(1)
unit = str(match.group(2)) # PhysicalQuantity doesn't like Unicode strings
if quantity_re.match(expr):
expr = 'Quantity(\'' + expr + '\')'
elif not expr:
expr = '_'
else:
expr = '(' + expr + ')'
if unit == 'base':
return '(' + expr + ').base'
if unit == 'cgs':
return '(' + expr + ').cgs'
else:
return 'Quantity.any_to(%s, %r)' % (expr, unit)
def replace_assign(match):
"""Replace a pretty assignment, e.g. ``B = 1 T``, by valid Python code using
a Quantity call.
"""
return '%s = Quantity(\'%s\')' % (match.group(1), match.group(2))
class QTransformer(object):
"""IPython command line transformer that recognizes and replaces unit
expressions.
"""
# XXX: inheriting from PrefilterTransformer as documented gives TypeErrors,
# but apparently is not needed after all
priority = 99
enabled = True
def transform(self, line, continue_prompt):
line = inline_unit_re.sub(replace_inline, line)
if not continue_prompt:
line = slash_conv_re.sub(replace_slash, line)
line = nice_assign_re.sub(replace_assign, line)
# lines that look like ``(/, unit)`` have been ``// unit`` but
# already preprocessed by IPython, let's recognize them
line = slash_last_re.sub(replace_slash, line)
return line
def input_transformer(lines):
new_lines = []
for line in lines:
line = inline_unit_re.sub(replace_inline, line)
line = slash_conv_re.sub(replace_slash, line)
line = nice_assign_re.sub(replace_assign, line)
# lines that look like ``(/, unit)`` have been ``// unit`` but
# already preprocessed by IPython, let's recognize them
line = slash_last_re.sub(replace_slash, line)
new_lines.append(line)
return new_lines
class QInputTransformer(InputTransformer):
def push(self, line):
return input_transformer([line])[0]
def reset(self):
pass
def tbl_magic(shell, arg):
"""tbl <expr>: Evaluate <expr> for a range of parameters, given
as "?name" in the expr.
"""
unit = None
match = trailing_conv_re.search(arg)
if match:
arg = arg[:match.start()]
unit = match.group(1)
substs = sorted(set(subst_re.findall(arg)))
if not substs:
raise ValueError('no substitutions in expr')
while 1:
expr = arg
for subst in substs:
try:
val = input('%s = ' % subst)
except EOFError:
sys.stdout.write('\n')
return
if not val:
return
if quantity_re.match(val):
val = '(' + val + ')'
expr = expr.replace('?' + subst, val)
if unit:
expr = 'Quantity.any_to((' + expr + '), %r)' % unit
if hasattr(shell, 'shell'): # later IPython versions
shell.shell.run_cell(expr, False)
else:
shell.run_cell(expr, False)
q_transformer = QTransformer()
def load_ipython_extension(ip):
# set up simplified quantity input
ip.user_ns['Q'] = Q
ip.user_ns['Quantity'] = Q
ip.prefilter_manager.register_transformer(q_transformer)
# add notebook transformers
try:
import IPython.core.inputtransformer2
except ImportError:
ip.input_transformer_manager.logical_line_transforms.append(
QInputTransformer())
else:
# IPython 7
ip.input_transformer_manager.line_transforms.append(input_transformer)
# setter for custom precision
ip.user_ns['setprec'] = \
lambda p: setattr(PhysicalQuantity, 'global_precision', p)
# quick evaluator
# TODO: this old API is no longer supported by IPython.
# Need to adapt it to the @register_line_magic API.
if hasattr(ip, 'define_magic'):
ip.define_magic('tbl', tbl_magic)
# add constants of nature
for const, value in _constants:
ip.user_ns[const] = value
print('Unit calculation and physics extensions activated.')
def unload_ipython_extension(ip):
ip.prefilter_manager.unregister_transformer(q_transformer)