arcgis python 随机取部分数据

# -*- coding: cp936 -*-
import arcpy
import os
import ylpy
import random
def main():
    num=ylpy.getCount(inFeature)
    n=int(num*mscale/100)
    ylpy.clearselect(inFeature)
    A=random.sample(range(num),n)
    FID=ylpy.getOIDField(inFeature)
    sql=str(FID)+" in ("
    for i in range(0,n):
        sql=sql+str(A[i])
        if i<n-1:
            sql=sql+","
    sql=sql+")"
    arcpy.Select_analysis(inFeature,outFeature,sql)


inFeature = arcpy.GetParameterAsText(0) #
mscale = arcpy.GetParameter(1) #
outFeature = arcpy.GetParameterAsText(2) #


try:
    main()
    #arcpy.SetParameterAsText(3, inFeature)  # Is polygon
except Exception, ErrorDesc:
    arcpy.AddError(u"gisoracle错误："+str(ErrorDesc))