输入参数作为查询语句Query 对Layer进行Select 报错！

# Import system modules

import arcpy

import os, shutil

import exceptions, sys, traceback

from arcpy import env

from arcpy.sa import *

import arcpy.mapping as mapping

reload(sys)

sys.setdefaultencoding('utf8') 



# Set environment settings

workSpacePath = arcpy.GetParameterAsText(0)

env.workspace = workSpacePath



# Enable overwrite output

env.overwriteOutput = True



# Set local variables

mxd = mapping.MapDocument("CURRENT")

df = mapping.ListDataFrames(mxd, "Layers")[0]



inCAD = arcpy.GetParameterAsText(1)



outShpsName = "outShp"

if not os.path.exists(outShpsName):

    outShpsFolder = os.path.join(workSpacePath, outShpsName)

    os.mkdir(outShpsFolder)



outLyrsName = "outLyr"

if not os.path.exists(outLyrsName):

    outLyrsFolder = os.path.join(workSpacePath, outLyrsName)

    os.mkdir(outLyrsFolder)



outFCsPath = arcpy.GetParameterAsText(2)

outFCsName = "outFC"

if outFCsPath == '#' or not outFCsPath:

    outFCsFolder = os.path.join(workSpacePath, outFCsName)

    os.mkdir(outFCsFolder)

else:

    outFCsFolder = outFCsPath



# Import elevation featureclasses

env.workspace = inCAD

fCs = arcpy.ListFeatureClasses("*")



for fc in fCs:

    arcpy.FeatureClassToShapefile_conversion(fc, outFCsFolder)



env.workspace = workSpacePath



# Switch elvation feature classes and generate layers

inPoint = workSpacePath + r"\outFC\Point.shp"

inPolyline = workSpacePath + r"\outFC\Polyline.shp"



elevQry =  arcpy.GetParameterAsText(3)



outPtFC = workSpacePath + r"\outShp\elevPoint"

outPtLayer = workSpacePath + r"\outLyr\elevPoint.lyr"

outPlFC = workSpacePath + r"\outShp\elevPolyline"

outPlLayer = workSpacePath + r"\outLyr\elevPolyline.lyr"

ptLayer = "elevPoint"

plLayer = "elevPolyline"



arcpy.MakeFeatureLayer_management(inPoint, ptLayer)

arcpy.SelectLayerByAttribute_management(ptLayer, "NEW_SELECTION", elevQry)

if int(arcpy.GetCount_management(ptLayer).getOutput(0)) > 0:

    arcpy.DeleteFeatures_management(ptLayer)

arcpy.SaveToLayerFile_management(ptLayer, outPtLayer, "ABSOLUTE")

arcpy.CopyFeatures_management(ptLayer, outPtFC)



arcpy.MakeFeatureLayer_management(inPolyline, plLayer)

arcpy.SelectLayerByAttribute_management(plLayer, "NEW_SELECTION", elevQry)

if int(arcpy.GetCount_management(plLayer).getOutput(0)) > 0:

    arcpy.DeleteFeatures_management(plLayer)

arcpy.SaveToLayerFile_management(plLayer, outPlLayer, "ABSOLUTE")

arcpy.CopyFeatures_management(plLayer, outPlFC)



layer1 = mapping.Layer(workSpacePath + r"\outLyr\elevPoint.lyr")

layer2 = mapping.Layer(workSpacePath + r"\outLyr\elevPolyline.lyr")



mapping.AddLayer(df, layer1)

mapping.AddLayer(df, layer2)

如上代码，想根据CAD提取出的高程数据通过SelectLayerByAttribute函数筛选出一些点并删除，但是执行完上面的代码后导出的图层会把其中的点线全删除（全部选定），查询语句没法正确应用于选择，Toolbox设置的输入参数为SQL expression，查询语句输入格式类似“Elevation” <= 600, 但若直接定义elevQry = ‘“Elevation” <= 600’ 则可正确执行，请问是为什么？应该如何解决？