Summary
Each part of the spatial reference has a number of properties (especially the coordinate system) that defines what map projection options are used to define horizontal coordinates.
Discussion
A SpatialReference object can also be accessed from existing datasets using the Describe spatialReference property.
dataset = "c:/data/landbase.gdb/Wetlands"
spatial_ref = arcpy.Describe(dataset).spatialReference
XY, Z, and M extents are not the same as spatial reference domains. The XY, Z, and M domains in a spatial reference define the valid range of coordinate values that can be stored in a feature class. The feature class extents reflect the actual range of coordinate values that exist in the feature class. These extents cannot be larger than the domains.
Note:
The spatial reference properties available depend on the coordinate system used. In the properties list below, those properties that are only available with a projected coordinate system are denoted with a ^{1}; properties only available with a geographic coordinate system are denoted with a ^{2}.
Because a projected coordinate system is based on a geographic coordinate system, projected coordinate system properties can be accessed from a geographic coordinate system via the GCS property.
Syntax
SpatialReference ({item}, {vcs}, text)
Parameter  Explanation  Data Type 
item  The horizontal coordinate system used to create the SpatialReference. The coordinate system can be set using a projection file, name, or factory code.
For more information about coordinate system names and factory codes, see the geographic_coordinate_systems.pdf and projected_coordinate_systems.pdf files. For more information, see Using the spatial reference class.  Variant 
vcs  The vertical coordinate system (VCS). The VCS defines information about the zcoordinates, and can be set using a name or factory code. See the following examples:
 Variant 
text  A wellknown text (WKT) string that can be used to define a horizontal and vertical coordinate system.
 String 
Properties
Property  Explanation  Data Type 
GCS (Read Only)  A projected coordinate system returns a SpatialReference object for the geographic coordinate system it is based on. A geographic coordinate system returns the same SpatialReference.  SpatialReference 
MDomain (Read Only)  The extent of the measure domain.  String 
MFalseOriginAndUnits (Read Only)  The measure false origin and units.  String 
MResolution (Read and Write)  The measure resolution.  Double 
MTolerance (Read and Write)  The measure tolerance.  Double 
VCS (Read Only)  If the coordinate system has a vertical coordinate system, it returns a VCS object for the vertical coordinate system it is based on.  Object 
XYResolution (Read and Write)  The xy resolution.  Double 
XYTolerance (Read and Write)  The xy tolerance.  Double 
ZDomain (Read Only)  The extent of the z domain.  String 
ZFalseOriginAndUnits (Read Only)  The z false origin and units.  String 
ZResolution (Read and Write)  The z resolution property.  Double 
ZTolerance (Read and Write)  The ztolerance property.  Double 
abbreviation (Read and Write)  The abbreviated name of the spatial reference.  String 
alias (Read and Write)  The alias of the spatial reference.  String 
domain (Read Only)  The extent of the xy domain.  String 
factoryCode (Read and Write)  The factory code or wellknown ID (WKID) of the spatial reference.  Integer 
falseOriginAndUnits (Read Only)  The false origin and units.  String 
hasMPrecision (Read Only)  Indicates whether mvalue precision information has been defined.  Boolean 
hasXYPrecision (Read Only)  Indicates whether xy precision information has been defined.  Boolean 
hasZPrecision (Read Only)  Indicates whether zvalue precision information has been defined.  Boolean 
isHighPrecision (Read and Write)  Indicates whether the spatial reference has high precision set.  Boolean 
name (Read and Write)  The name of the spatial reference.  String 
remarks (Read and Write)  The comment string of the spatial reference.  String 
type (Read and Write)  The type of the spatial reference.
 String 
usage (Read Only)  The usage notes.  String 
PCSCode (Read and Write)  The projected coordinate system code.^{1}  Integer 
PCSName (Read and Write)  The projected coordinate system name.^{1}  String 
azimuth (Read and Write)  The azimuth of a projected coordinate system.^{1}  Double 
centralMeridian (Read and Write)  The central meridian of a projected coordinate system.^{1}  Double 
centralMeridianInDegrees (Read and Write)  The central meridian (Lambda0) of a projected coordinate system in degrees.^{1}  Double 
centralParallel (Read and Write)  The central parallel of a projected coordinate system.^{1}  Double 
classification (Read Only)  The classification of a map projection.^{1}  String 
falseEasting (Read and Write)  The false easting of a projected coordinate system.^{1}  Double 
falseNorthing (Read and Write)  The false northing of a projected coordinate system.^{1}  Double 
latitudeOf1st (Read and Write)  The latitude of the first point of a projected coordinate system.^{1}  Double 
latitudeOf2nd (Read and Write)  The latitude of the second point of a projected coordinate system.^{1}  Double 
latitudeOfOrigin (Read and Write)  The latitude of origin of a projected coordinate system.^{1}  Double 
linearUnitCode (Read and Write)  The linear unit code.^{1}  Integer 
linearUnitName (Read and Write)  The linear unit name.^{1}  String 
longitude (Read and Write)  The longitude value of this prime meridian.^{1}  Double 
longitudeOf1st (Read and Write)  The longitude of the first point of a projected coordinate system.^{1}  Double 
longitudeOf2nd (Read and Write)  The longitude of the second point of a projected coordinate system.^{1}  Double 
longitudeOfOrigin (Read and Write)  The longitude of origin of a projected coordinate system.^{1}  Double 
metersPerUnit (Read Only)  The meters per linear unit.^{1}  Double 
projectionCode (Read and Write)  The projection code.^{1}  Integer 
projectionName (Read and Write)  The projection name.^{1}  String 
scaleFactor (Read and Write)  The scale factor of a projected coordinate system.^{1}  Double 
standardParallel1 (Read and Write)  The first parallel of a projected coordinate system.^{1}  Double 
standardParallel2 (Read and Write)  The second parallel of a projected coordinate system.^{1}  Double 
GCSCode (Read and Write)  The geographic coordinate system code.^{2}  Integer 
GCSName (Read and Write)  The geographic coordinate system name.^{2}  String 
angularUnitCode (Read and Write)  The angular unit code.^{2}  Integer 
angularUnitName (Read and Write)  The angular unit name.^{2}  String 
datumCode (Read and Write)  The datum code.^{2}  Integer 
datumName (Read and Write)  The datum name.^{2}  String 
flattening (Read and Write)  The flattening ratio of this spheroid.^{2}  Double 
longitude (Read and Write)  The longitude value of this prime meridian.^{2}  Double 
primeMeridianCode (Read and Write)  The prime meridian code.^{2}  Integer 
primeMeridianName (Read and Write)  The prime meridian name.^{2}  String 
radiansPerUnit (Read Only)  The radians per angular unit.^{2}  Double 
semiMajorAxis (Read and Write)  The semimajor axis length of this spheroid.^{2}  Double 
semiMinorAxis (Read and Write)  The semiminor axis length of this spheroid.^{2}  Double 
spheroidCode (Read and Write)  The spheroid code.^{2}  Integer 
spheroidName (Read and Write)  The spheroid name.^{2}  String 
Method Overview
Method  Explanation 
create ()  Creates the SpatialReference object using properties. 
createFromFile (prj_file)  Creates the SpatialReference object from a projection file. 
exportToString ()  Exports the object to its string representation. 
loadFromString (string)  Restore or update the spatial reference object using a WKT string. The exportToString method can be used to export a WKT string representation of the spatial reference.

setDomain (x_min, x_max, y_min, y_max)  Sets the XY domain. 
setFalseOriginAndUnits (false_x, false_y, xy_units)  Sets the XY false origin and units. 
setMDomain (m_min, m_max)  Sets the M domain. 
setMFalseOriginAndUnits (false_m, m_units)  Sets the M false origin and units. 
setZDomain (z_min, z_max)  Sets the Z domain. 
setZFalseOriginAndUnits (false_z, z_units)  Sets the Z false origin and units. 
Methods
create ()
createFromFile (prj_file)
Parameter  Explanation  Data Type 
prj_file  The projection file used to populate the SpatialReference object.  String 
exportToString ()
Data Type  Explanation 
String  The WKT string representation of the object. 
loadFromString (string)
Parameter  Explanation  Data Type 
string  The WKT string representation of the object.  String 
setDomain (x_min, x_max, y_min, y_max)
Parameter  Explanation  Data Type 
x_min  The minimum xvalue.  Double 
x_max  The maximum xvalue.  Double 
y_min  The minimum yvalue.  Double 
y_max  The maximum yvalue.  Double 
setFalseOriginAndUnits (false_x, false_y, xy_units)
Parameter  Explanation  Data Type 
false_x  The false x value.  Double 
false_y  The false y value.  Double 
xy_units  The xy units.  String 
setMDomain (m_min, m_max)
Parameter  Explanation  Data Type 
m_min  The minimum mvalue.  Double 
m_max  The maximum mvalue.  Double 
setMFalseOriginAndUnits (false_m, m_units)
Parameter  Explanation  Data Type 
false_m  The false mvalue.  Double 
m_units  The m units.  Double 
setZDomain (z_min, z_max)
Parameter  Explanation  Data Type 
z_min  The minimum zvalue.  Double 
z_max  The maximum zvalue.  Double 
setZFalseOriginAndUnits (false_z, z_units)
Parameter  Explanation  Data Type 
false_z  The false zvalue.  Double 
z_units  The false z units.  Double 
Code sample
For each feature class in a workspace, print the name of its spatial reference.
import arcpy
# Set the workspace environment
arcpy.env.workspace = "c:/base/base.gdb"
# Get a list of the feature classes in the input folder
feature_classes = arcpy.ListFeatureClasses()
# Loop through the list
for fc in feature_classes:
# Create the spatial reference object
spatial_ref = arcpy.Describe(fc).spatialReference
# If the spatial reference is unknown
if spatial_ref.name == "Unknown":
print("{} has an unknown spatial reference".format(fc))
# Otherwise, print out the feature class name and spatial reference
else:
print("{} : {}".format(fc, spatial_ref.name))