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units example code: basic_units.pyΒΆ

(Source code)

import math

import numpy as np

import matplotlib.units as units
import matplotlib.ticker as ticker
from matplotlib.axes import Axes
from matplotlib.cbook import iterable

class ProxyDelegate(object):
    def __init__(self, fn_name, proxy_type):
        self.proxy_type = proxy_type
        self.fn_name = fn_name

    def __get__(self, obj, objtype=None):
        return self.proxy_type(self.fn_name, obj)

class TaggedValueMeta (type):
    def __init__(cls, name, bases, dict):
        for fn_name in cls._proxies.keys():
                dummy = getattr(cls, fn_name)
            except AttributeError:
                setattr(cls, fn_name,
                        ProxyDelegate(fn_name, cls._proxies[fn_name]))

class PassThroughProxy(object):
    def __init__(self, fn_name, obj):
        self.fn_name = fn_name = obj.proxy_target

    def __call__(self, *args):
        fn = getattr(, self.fn_name)
        ret = fn(*args)
        return ret

class ConvertArgsProxy(PassThroughProxy):
    def __init__(self, fn_name, obj):
        PassThroughProxy.__init__(self, fn_name, obj)
        self.unit = obj.unit

    def __call__(self, *args):
        converted_args = []
        for a in args:
            except AttributeError:
                converted_args.append(TaggedValue(a, self.unit))
        converted_args = tuple([c.get_value() for c in converted_args])
        return PassThroughProxy.__call__(self, *converted_args)

class ConvertReturnProxy(PassThroughProxy):
    def __init__(self, fn_name, obj):
        PassThroughProxy.__init__(self, fn_name, obj)
        self.unit = obj.unit

    def __call__(self, *args):
        ret = PassThroughProxy.__call__(self, *args)
        if (type(ret) == type(NotImplemented)):
            return NotImplemented
        return TaggedValue(ret, self.unit)

class ConvertAllProxy(PassThroughProxy):
    def __init__(self, fn_name, obj):
        PassThroughProxy.__init__(self, fn_name, obj)
        self.unit = obj.unit

    def __call__(self, *args):
        converted_args = []
        arg_units = [self.unit]
        for a in args:
            if hasattr(a, 'get_unit') and not hasattr(a, 'convert_to'):
                # if this arg has a unit type but no conversion ability,
                # this operation is prohibited
                return NotImplemented

            if hasattr(a, 'convert_to'):
                    a = a.convert_to(self.unit)
                if hasattr(a, 'get_unit'):
        converted_args = tuple(converted_args)
        ret = PassThroughProxy.__call__(self, *converted_args)
        if (type(ret) == type(NotImplemented)):
            return NotImplemented
        ret_unit = unit_resolver(self.fn_name, arg_units)
        if (ret_unit == NotImplemented):
            return NotImplemented
        return TaggedValue(ret, ret_unit)

class _TaggedValue(object):

    _proxies = {'__add__': ConvertAllProxy,
                '__sub__': ConvertAllProxy,
                '__mul__': ConvertAllProxy,
                '__rmul__': ConvertAllProxy,
                '__cmp__': ConvertAllProxy,
                '__lt__': ConvertAllProxy,
                '__gt__': ConvertAllProxy,
                '__len__': PassThroughProxy}

    def __new__(cls, value, unit):
        # generate a new subclass for value
        value_class = type(value)
            subcls = type('TaggedValue_of_%s' % (value_class.__name__),
                          tuple([cls, value_class]),
            if subcls not in units.registry:
                units.registry[subcls] = basicConverter
            return object.__new__(subcls)
        except TypeError:
            if cls not in units.registry:
                units.registry[cls] = basicConverter
            return object.__new__(cls)

    def __init__(self, value, unit):
        self.value = value
        self.unit = unit
        self.proxy_target = self.value

    def __getattribute__(self, name):
        if (name.startswith('__')):
            return object.__getattribute__(self, name)
        variable = object.__getattribute__(self, 'value')
        if (hasattr(variable, name) and name not in self.__class__.__dict__):
            return getattr(variable, name)
        return object.__getattribute__(self, name)

    def __array__(self, t=None, context=None):
        if t is not None:
            return np.asarray(self.value).astype(t)
            return np.asarray(self.value, 'O')

    def __array_wrap__(self, array, context):
        return TaggedValue(array, self.unit)

    def __repr__(self):
        return 'TaggedValue(' + repr(self.value) + ', ' + repr(self.unit) + ')'

    def __str__(self):
        return str(self.value) + ' in ' + str(self.unit)

    def __len__(self):
        return len(self.value)

    def __iter__(self):
        class IteratorProxy(object):
            def __init__(self, iter, unit):
                self.iter = iter
                self.unit = unit

            def __next__(self):
                value = next(self.iter)
                return TaggedValue(value, self.unit)
            next = __next__  # for Python 2
        return IteratorProxy(iter(self.value), self.unit)

    def get_compressed_copy(self, mask):
        new_value =, mask=mask).compressed()
        return TaggedValue(new_value, self.unit)

    def convert_to(self, unit):
        if (unit == self.unit or not unit):
            return self
        new_value = self.unit.convert_value_to(self.value, unit)
        return TaggedValue(new_value, unit)

    def get_value(self):
        return self.value

    def get_unit(self):
        return self.unit

TaggedValue = TaggedValueMeta('TaggedValue', (_TaggedValue, ), {})

class BasicUnit(object):
    def __init__(self, name, fullname=None): = name
        if fullname is None:
            fullname = name
        self.fullname = fullname
        self.conversions = dict()

    def __repr__(self):
        return 'BasicUnit(%s)' %

    def __str__(self):
        return self.fullname

    def __call__(self, value):
        return TaggedValue(value, self)

    def __mul__(self, rhs):
        value = rhs
        unit = self
        if hasattr(rhs, 'get_unit'):
            value = rhs.get_value()
            unit = rhs.get_unit()
            unit = unit_resolver('__mul__', (self, unit))
        if (unit == NotImplemented):
            return NotImplemented
        return TaggedValue(value, unit)

    def __rmul__(self, lhs):
        return self*lhs

    def __array_wrap__(self, array, context):
        return TaggedValue(array, self)

    def __array__(self, t=None, context=None):
        ret = np.array([1])
        if t is not None:
            return ret.astype(t)
            return ret

    def add_conversion_factor(self, unit, factor):
        def convert(x):
            return x*factor
        self.conversions[unit] = convert

    def add_conversion_fn(self, unit, fn):
        self.conversions[unit] = fn

    def get_conversion_fn(self, unit):
        return self.conversions[unit]

    def convert_value_to(self, value, unit):
        conversion_fn = self.conversions[unit]
        ret = conversion_fn(value)
        return ret

    def get_unit(self):
        return self

class UnitResolver(object):
    def addition_rule(self, units):
        for unit_1, unit_2 in zip(units[:-1], units[1:]):
            if (unit_1 != unit_2):
                return NotImplemented
        return units[0]

    def multiplication_rule(self, units):
        non_null = [u for u in units if u]
        if (len(non_null) > 1):
            return NotImplemented
        return non_null[0]

    op_dict = {
        '__mul__': multiplication_rule,
        '__rmul__': multiplication_rule,
        '__add__': addition_rule,
        '__radd__': addition_rule,
        '__sub__': addition_rule,
        '__rsub__': addition_rule}

    def __call__(self, operation, units):
        if (operation not in self.op_dict):
            return NotImplemented

        return self.op_dict[operation](self, units)

unit_resolver = UnitResolver()

cm = BasicUnit('cm', 'centimeters')
inch = BasicUnit('inch', 'inches')
inch.add_conversion_factor(cm, 2.54)
cm.add_conversion_factor(inch, 1/2.54)

radians = BasicUnit('rad', 'radians')
degrees = BasicUnit('deg', 'degrees')
radians.add_conversion_factor(degrees, 180.0/np.pi)
degrees.add_conversion_factor(radians, np.pi/180.0)

secs = BasicUnit('s', 'seconds')
hertz = BasicUnit('Hz', 'Hertz')
minutes = BasicUnit('min', 'minutes')

secs.add_conversion_fn(hertz, lambda x: 1./x)
secs.add_conversion_factor(minutes, 1/60.0)

# radians formatting
def rad_fn(x, pos=None):
    n = int((x / np.pi) * 2.0 + 0.25)
    if n == 0:
        return '0'
    elif n == 1:
        return r'$\pi/2$'
    elif n == 2:
        return r'$\pi$'
    elif n % 2 == 0:
        return r'$%s\pi$' % (n//2,)
        return r'$%s\pi/2$' % (n,)

class BasicUnitConverter(units.ConversionInterface):
    def axisinfo(unit, axis):
        'return AxisInfo instance for x and unit'

        if unit == radians:
            return units.AxisInfo(
        elif unit == degrees:
            return units.AxisInfo(
        elif unit is not None:
            if hasattr(unit, 'fullname'):
                return units.AxisInfo(label=unit.fullname)
            elif hasattr(unit, 'unit'):
                return units.AxisInfo(label=unit.unit.fullname)
        return None

    def convert(val, unit, axis):
        if units.ConversionInterface.is_numlike(val):
            return val
        if iterable(val):
            return [thisval.convert_to(unit).get_value() for thisval in val]
            return val.convert_to(unit).get_value()

    def default_units(x, axis):
        'return the default unit for x or None'
        if iterable(x):
            for thisx in x:
                return thisx.unit
        return x.unit

def cos(x):
    if iterable(x):
        return [math.cos(val.convert_to(radians).get_value()) for val in x]
        return math.cos(x.convert_to(radians).get_value())

basicConverter = BasicUnitConverter()
units.registry[BasicUnit] = basicConverter
units.registry[TaggedValue] = basicConverter

Keywords: python, matplotlib, pylab, example, codex (see Search examples)