def __pow__(self, other):
if self.offset != 0:
raise TypeError("cannot exponentiate units with non-zero offset")
if isinstance(other, int):
return PhysicalUnit(other * self.names, pow(self.factor, other),
map(lambda x, p=other: x * p, self.powers))
if isinstance(other, float):
inv_exp = 1. / other
rounded = int(N.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 = map(lambda x, p=rounded: x / p, 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 TypeError('Illegal exponent')
raise TypeError('Only integer and inverse integer exponents allowed')
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.
@type names: C{dict} or C{str}
@param factor: a scaling factor
@type factor: C{float}
@param powers: the integer powers for each of the nine base units
@type powers: C{list} of C{int}
@param offset: an additive offset to the base unit (used only for
temperatures)
@type offset: C{float}
"""
if type(names) == type(''):
self.names = NumberDict()
self.names[names] = 1
pass
else:
self.names = names
pass
self.factor = factor
self.offset = offset
self.powers = powers
def setName(self, name):
self.names = NumberDict()
self.names[name] = 1