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# Quantities with units
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# This file's encoding must be UTF-8Y with BOM so Python will auto-detect UTF-8
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import re
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import format
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import strings
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import util
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def parse_range(str_, range_sep='-'):
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default = (str_, None)
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start, sep, end = str_.partition(range_sep)
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if sep == '': return default # not a range
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if start == '' and range_sep == '-': return default # negative number
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return tuple(d.strip() for d in (start, end))
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class MissingUnitsException(Exception):
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def __init__(self, quantity):
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Exception.__init__(self, 'Quantity has no units: '
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+strings.ustr(quantity))
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def std_units(units):
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if units == None: return units
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else: return strings.remove_suffix('.', units) # for abbr ending in '.'
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# TODO: deal with '"° and abbrs
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class Quantity:
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def __init__(self, value='', units=None):
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self.value = value
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self.units = std_units(util.none_if(units, u''))
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def quantity2str(quantity):
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str_ = quantity.value
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if quantity.units != None: str_ += ' '+quantity.units
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return str_
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Quantity.__str__ = quantity2str
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Quantity.__repr__ = quantity2str
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def str2quantity(str_):
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value = str_
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units = None
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if not str_.isdigit(): # optimization to avoid regexp for simple cases
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match = re.match(ur'(?i)^\s*(.*?\d\.?)\s*([a-z%\'"°][\w.*/^-]*?)?\s*$',
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str_)
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if match: value, units = match.groups() # has units
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return Quantity(value, units)
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def set_default_units(quantity, units):
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if quantity.units == None: quantity.units = units
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conversions = {
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('%', None): 1./100,
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('ft', 'm'): 12*2.54/100,
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}
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def convert(quantity, units):
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units = std_units(units)
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if quantity.units == units: return quantity # units already correct
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try: conversion = conversions[(quantity.units, units)]
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except KeyError:
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if units == None: return Quantity(quantity.value, units) # remove units
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elif quantity.units == None: raise MissingUnitsException(quantity)
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# can't convert quantity with unknown units
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else: raise NotImplementedError('Unit conversion not implemented yet')
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else:
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for try_num in xrange(2):
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try:
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value = format.str2float(quantity.value)
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break
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except ValueError: quantity.value = parse_range(quantity.value)[0]
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return Quantity(str(value*conversion), units)
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