一、使用代码块简介

        举例见下图

 上例：将多边形几何面积取一位小数写入【TBYBH】字段

二、常用功能块
1、自动序号
     调用表达式：num()
    块代码：     

star= 0
def num():
  global star
  star+=1
  return star

2、按地类名称字段值，对地类代码字段赋值，代码块名称为：DLZH
      调用表达式：DLZH(!DLMC!)
      块代码：

def DLZH(x):
    if x==u"水田":
        return "0101"
    elif x==u"水浇地":
        return "0102"
    elif x==u"旱地":
        return "0103"
    else:
        return "非耕地"

3、按地类代码进行土地三大类分类，代码块名称为：DL3DL
      DL3DL(!DLBM!)

def DL3DL(DLFL):
    if (DLFL =="0101" or DLFL =="0102" or DLFL =="0103" ):
        return "耕地"
    elif (DLFL == "0201" or DLFL =="0202" or DLFL =="0203" or DLFL =="0204" or DLFL =="0301" or DLFL =="0301" or DLFL =="0302" or DLFL =="0303" or DLFL =="0304" or DLFL =="0305" or DLFL =="0306" or DLFL =="0307" or DLFL =="0401" or DLFL =="0402" or DLFL =="0403" or DLFL =="1006" or DLFL =="1103" or DLFL =="1104"  or DLFL =="1107" or DLFL =="1202" or DLFL =="1203"):
        return "其他农用地"
    elif (DLFL == "05H1" or DLFL == "0508" or DLFL == "0601" or DLFL == "0602" or DLFL == "0603" or DLFL == "0701" or DLFL == "0702" or DLFL == "08H1" or DLFL == "08H2" or DLFL == "0809" or DLFL == "0810" or DLFL == "09" or DLFL == "1001" or DLFL == "1002" or DLFL == "1003" or DLFL == "1004" or DLFL == "1005" or DLFL == "1007" or DLFL == "1008" or DLFL == "1009" or DLFL == "1109" or DLFL == "1201"):
        return "建设用地"
    elif (DLFL == "0404" or DLFL == "1101" or DLFL == "1102" or DLFL == "1105" or DLFL == "1106" or DLFL == "1108" or DLFL == "1110" or DLFL == "1204" or DLFL == "1205" or DLFL == "1206" or DLFL == "1207"):
        return "未利用土地"
    else:
        return "没有对应关系地类"

4、计算某要素中的折点数。代码块名称为：getVertexCount

调用表达式：getVertexCount(!shape!)

def getVertexCount(feat):    
    partnum = 0
    partcount = feat.partCount
    pntcount = 0
    while partnum < partcount:
        part = feat.getPart(partnum)
        pnt = part.next()
        while pnt:
            pntcount += 1   
            pnt = part.next()
            if not pnt: 
                pnt = part.next()
        partnum += 1
    return pntcount

5、根据某间隔值计算顺序 ID 或数字，代码块名称：autoIncrement
表达式：autoIncrement(10, 5)     ，调用初始值为10，每次递增5

rec = 0
def autoIncrement(start=1, interval=1):
    global rec
    if rec == 0:
        rec = start
    else:
        rec += interval
    return rec