使用ArcPy获取图层符号系统？

由于ArcGIS 10随附了ArcPy软件包，因此我想知道是否可以使用ArcPy函数获取图层的符号系统（即颜色，宽度...）？

对于ArcGIS 10.0，如果可以使用只读方法，则以下代码示例将揭示构成图层符号系统基础的字段（和连接的表）。它导出一个临时msd（包含xml文件的zip文件），并将特定的属性加载到一个对象中。可以扩展这些类以获得对其他图层属性的访问。

import zipfile
from arcpy import mapping
import os
from xml.dom.minidom import parse


class LayerExtras(object):
    """ An object to hold attributes loaded from xml inside the msd."""

    name = ""
    symbologyFieldName = ""


class MxdExtras(dict):
    """ Exposes extra MXD details by raiding an exported msd

        Treat this object as a dictionary with layer name as the key and a custom object
        with desired attributes as the value.
        You must have write access to MXD directory (creates temporary msd file).
        Only layers in the first dataframe are accessed.

    """    

    LYR_NAME_NODE = "Name"
    LYR_SYMBOL_NODE = "Symbolizer"
    LYR_FIELD_NODE = "Field"
    MSD_SUFFIX = "_MxdExtrasTemp.msd"
    MXD_SUFFIX = ".mxd"
    EXCLUDED_FILE_NAMES = ["DocumentInfo.xml", "layers/layers.xml"]
    mxdPath = ""

    def __init__(self, mxdPath):

        self.loadMxdPath(mxdPath)


    def loadMxdPath(self, mxdPath):
        """ Load mxd from file path """

        self.mxdPath = mxdPath.lower()
        mxd = mapping.MapDocument(self.mxdPath)

        msdPath = self.mxdPath.replace(self.MXD_SUFFIX, self.MSD_SUFFIX) 

        # Delete temporary msd if it exists
        if os.path.exists(msdPath):
            os.remove(msdPath)

        mapping.ConvertToMSD(mxd,msdPath)

        zz = zipfile.ZipFile(msdPath)

        for fileName in (fileName for fileName in zz.namelist() if not fileName in self.EXCLUDED_FILE_NAMES):
            dom = parse(zz.open(fileName))
            name, lyr = self.loadMsdLayerDom(dom)
            self[name] = lyr
        del zz
        os.remove(msdPath)

    def loadMsdLayerDom(self, dom):
        """ Load dom created from xml file inside the msd. """

        lyr = LayerExtras()  

        # Layer name
        lyr.name = dom.getElementsByTagName(self.LYR_NAME_NODE)[0].childNodes[0].nodeValue

        # Symbology field name
        symbologyElement = dom.getElementsByTagName(self.LYR_SYMBOL_NODE)[0]
        lyr.symbologyFieldName = symbologyElement.getElementsByTagName(self.LYR_FIELD_NODE)[0].childNodes[0].nodeValue

        return lyr.name, lyr


############
# Test

if __name__ == "__main__":

    mxdPath = r"c:\temp\AmphibianSpeciesRichnessAverageOf30mCells.mxd"

    mxde = MxdExtras(mxdPath)

    for lyr in mxde.itervalues():
        print "Layer Name: ", lyr.name 
        print "Layer Symbology Field Name: ", lyr.symbologyFieldName
        print 

测试的示例输出：

Layer Name:  Amphibian Species Richness Average of 30m Cells
Layer Symbology Field Name:  biodiversity.AmphAve

ArcPy希望让您更改符号系统，但只能使用现有的.lyr文件，而不能根据我对模块的了解直接在代码中指定符号。

在ArcGIS 10.1和更高版本中，可以通过图层对象的symbology属性直接访问符号系统。

对于ArcGIS 10.0，上述解决方法确实对我有用。