The django.contrib.gis.measure module contains objects that allow
for convenient representation of distance and area units of measure. 1
Specifically, it implements two objects, Distance and
Area -- both of which may be accessed via the
D and A convenience aliases, respectively.
Distance objects may be instantiated using a keyword argument indicating the
context of the units. In the example below, two different distance objects are
instantiated in units of kilometers (km) and miles (mi):
>>> from django.contrib.gis.measure import D, Distance
>>> d1 = Distance(km=5)
>>> print(d1)
5.0 km
>>> d2 = D(mi=5) # `D` is an alias for `Distance`
>>> print(d2)
5.0 mi
For conversions, access the preferred unit attribute to get a converted distance quantity:
>>> print(d1.mi) # Converting 5 kilometers to miles
3.10685596119
>>> print(d2.km) # Converting 5 miles to kilometers
8.04672
Moreover, arithmetic operations may be performed between the distance objects:
>>> print(d1 + d2) # Adding 5 miles to 5 kilometers
13.04672 km
>>> print(d2 - d1) # Subtracting 5 kilometers from 5 miles
1.89314403881 mi
Two Distance objects multiplied together will yield an Area
object, which uses squared units of measure:
>>> a = d1 * d2 # Returns an Area object.
>>> print(a)
40.2336 sq_km
To determine what the attribute abbreviation of a unit is, the unit_attname
class method may be used:
>>> print(Distance.unit_attname('US Survey Foot'))
survey_ft
>>> print(Distance.unit_attname('centimeter'))
cm
| Unit Attribute | Full name or alias(es) |
|---|---|
km
|
Kilometre, Kilometer |
mi
|
Mile |
m
|
Meter, Metre |
yd
|
Yard |
ft
|
Foot, Foot (International) |
survey_ft
|
U.S. Foot, US survey foot |
inch
|
Inches |
cm
|
Centimeter |
mm
|
Millimetre, Millimeter |
um
|
Micrometer, Micrometre |
british_ft
|
British foot (Sears 1922) |
british_yd
|
British yard (Sears 1922) |
british_chain_sears
|
British chain (Sears 1922) |
indian_yd
|
Indian yard, Yard (Indian) |
sears_yd
|
Yard (Sears) |
clarke_ft
|
Clarke's Foot |
chain
|
Chain |
chain_benoit
|
Chain (Benoit) |
chain_sears
|
Chain (Sears) |
british_chain_benoit
|
British chain (Benoit 1895 B) |
british_chain_sears_truncated
|
British chain (Sears 1922 truncated) |
gold_coast_ft
|
Gold Coast foot |
link
|
Link |
link_benoit
|
Link (Benoit) |
link_sears
|
Link (Sears) |
clarke_link
|
Clarke's link |
fathom
|
Fathom |
rod
|
Rod |
furlong
|
Furlong, Furrow Long |
nm
|
Nautical Mile |
nm_uk
|
Nautical Mile (UK) |
german_m
|
German legal metre |
DistanceDistance(**kwargs)[源代码]To initialize a distance object, pass in a keyword corresponding to the desired unit attribute name set with desired value. For example, the following creates a distance object representing 5 miles:
>>> dist = Distance(mi=5)
__getattr__(unit_att)Returns the distance value in units corresponding to the given unit attribute. For example:
>>> print(dist.km)
8.04672
unit_attname(unit_name)Returns the distance unit attribute name for the given full unit name. For example:
>>> Distance.unit_attname('Mile')
'mi'
DDistance class.
AreaArea(**kwargs)[源代码]To initialize an area object, pass in a keyword corresponding to the desired unit attribute name set with desired value. For example, the following creates an area object representing 5 square miles:
>>> a = Area(sq_mi=5)
__getattr__(unit_att)Returns the area value in units corresponding to the given unit attribute. For example:
>>> print(a.sq_km)
12.949940551680001
unit_attname(unit_name)Returns the area unit attribute name for the given full unit name. For example:
>>> Area.unit_attname('Kilometer')
'sq_km'
AArea class.Footnotes