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>>> from django.contrib.gis.measure import Distance, D
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>>> d1 = Distance(km=5)
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>>> d2 = D(mi=5) # `D` is an alias for `Distance`
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Conversions are easy, just access the preferred unit attribute to get a
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converted distance quantity::
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>>> print d1.mi # Converting 5 kilometers to miles
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>>> print(d1.mi) # Converting 5 kilometers to miles
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>>> print d2.km # Converting 5 miles to kilometers
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>>> print(d2.km) # Converting 5 miles to kilometers
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Moreover, arithmetic operations may be performed between the distance
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>>> print d1 + d2 # Adding 5 miles to 5 kilometers
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>>> print(d1 + d2) # Adding 5 miles to 5 kilometers
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>>> print d2 - d1 # Subtracting 5 kilometers from 5 miles
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>>> print(d2 - d1) # Subtracting 5 kilometers from 5 miles
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Two :class:`Distance` objects multiplied together will yield an :class:`Area`
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object, which uses squared units of measure::
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>>> a = d1 * d2 # Returns an Area object.
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To determine what the attribute abbreviation of a unit is, the ``unit_attname``
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class method may be used::
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>>> print Distance.unit_attname('US Survey Foot')
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>>> print(Distance.unit_attname('US Survey Foot'))
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>>> print Distance.unit_attname('centimeter')
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>>> print(Distance.unit_attname('centimeter'))
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.. _supported_units: