ArcToolbox Tool: Add [ST_CON_ABR] to Hennepin County, MN Centerlines

One of the great advancements over the last decade plus in GIS is that government agencies have started to move away from a “recover-our-cost” mentality to more of an “Open Data”. Minnesota, for example, has launched their Geospatial Commons as a platform for sharing data.

And while getting free, authoritative data is awesome, it can leave you in a bind if the structure of the data changes. Sometime between April and September, Hennepin County, Minnesota, changed the schema of their publicly available street centerlines data.

The data used to have both a full, concatenated street name field ([ST_CONCAT]) and an abbreviated version ([ST_CON_ABR]). A record might have “James Lofton Avenue North” and “James Lofton Ave N”, respectively, in these two fields. The abbreviated version was nice for labeling but it disappeared from the most recent updates.

So, as you  might guess from the fact that I’m posting about it, I wrote a script to add that field in and launch it from an ArcToolbox Tool. Nothing fancy going on in the code, just a series of replaces, depending on the field. Using dictionaries instead of arrays of paired values might have been better but the script takes just a few seconds to run so I can live with it as-is.

The list of street type abbreviations came from a combination of ESRI’s standards and those found in an older version of the Hennepin County data. There were no conflicting abbreviations between the two. The code warns if a street name occurs in the data that is not in the list.

While I’m including the code here for reference, it’s probably best to download the code from GitHub.

#-------------------------------------------------------------------------------
# Name:        usi_dataprep_Add_STCONABR
#
# Purpose:     This can be used to add [CT_CON_ABR] to Hennepin County, MN
#              centerlines. This is a concatenated, abbreviated full name of
#              the street. This used to be included in the data but
#              disappeared from the downloads in the summer of 2017.
#
#              Data available at: http://www.hennepin.us/gisopendata
#
# Author:      mrantala
#
# Created:     2017.10.04
#
#------------------------------------------------------------------------------

import arcpy

############################################
## Custom Variables
#These are the fields that are concatenated. Hennepin has others but were always blank.
requiredFieldList = ["ST_PRE_DIR","ST_PRE_TYP","ST_NAME","ST_POS_TYP","ST_POS_DIR"]
#This is the name of the field to add
newFieldName = "ST_CON_ABR"

#These are the abbreviations for [ST_POS_TYPE]. The list was created using a sample of
#Hennepin's centerline data & Esri Tech article: http://support.esri.com/en/technical-article/000008454
# Note that I intentionally left cases in where there is no abbreviation (Fall, for example) as a means of
#documenting the fact that it should NOT change.

abbList = []
abbList.append(["Alcove","Alcove"]) #Hennepin Specific
abbList.append(["Alley","Aly"])
abbList.append(["Annex","Anx"])
abbList.append(["Arcade","Arc"])
abbList.append(["Avenue","Ave"])
abbList.append(["Bay","Bay"]) #Hennepin Specific
abbList.append(["Bayoo","Byu"])
abbList.append(["Beach","Bch"])
abbList.append(["Bend","Bnd"])
abbList.append(["Bluff","Blf"])
abbList.append(["Bluffs","Blfs"])
abbList.append(["Bottom","Btm"])
abbList.append(["Boulevard","Blvd"])
abbList.append(["Branch","Br"])
abbList.append(["Bridge","Brg"])
abbList.append(["Brook","Brk"])
abbList.append(["Brooks","Brks"])
abbList.append(["Burg","Bg"])
abbList.append(["Burgs","Bgs"])
abbList.append(["Bypass","Byp"])
abbList.append(["Camp","Cp"])
abbList.append(["Canyon","Cyn"])
abbList.append(["Cape","Cpe"])
abbList.append(["Causeway","Cswy"])
abbList.append(["Center","Ctr"])
abbList.append(["Centers","Ctrs"])
abbList.append(["Crossings","Crossings"]) #Hennepin Specific
abbList.append(["Crossroad","Xrd"])
abbList.append(["Chase","Chase"]) #Hennepin Specific
abbList.append(["Circle","Cir"])
abbList.append(["Circles","Cirs"])
abbList.append(["Cliff","Clf"])
abbList.append(["Cliffs","Clfs"])
abbList.append(["Club","Clb"])
abbList.append(["Close","Close"]) #Hennepin Specific
abbList.append(["Common","Cmn"])
abbList.append(["Commons","Cmns"]) #Hennepin Specific
abbList.append(["Corner","Cor"])
abbList.append(["Corners","Cors"])
abbList.append(["Corridor","Corridor"]) #Hennepin Specific
abbList.append(["Course","Crse"])
abbList.append(["Court","Ct"])
abbList.append(["Courts","Cts"])
abbList.append(["Cove","Cv"])
abbList.append(["Coves","Cvs"])
abbList.append(["Creek","Crk"])
abbList.append(["Crescent","Cres"])
abbList.append(["Crest","Crst"])
abbList.append(["Cross","Cross"]) #Hennepin Specific
abbList.append(["Crossing","Xing"])
abbList.append(["Curve","Curve"])
abbList.append(["Dale","Dl"])
abbList.append(["Dam","Dm"])
abbList.append(["Divide","Dv"])
abbList.append(["Down","Down"]) #Hennepin Specific
abbList.append(["Downs","Downs"]) #Hennepin Specific
abbList.append(["Drive","Dr"])
abbList.append(["Drives","Drs"])
abbList.append(["Edge","Edge"]) #Hennepin Specific
abbList.append(["Entry","Entry"]) #Hennepin Specific
abbList.append(["Estate","Est"])
abbList.append(["Estates","Ests"])
abbList.append(["Expressway","Expy"])
abbList.append(["Extension","Ext"])
abbList.append(["Extensions","Exts"])
abbList.append(["Fall","Fall"])
abbList.append(["Falls","Fls"])
abbList.append(["Ferry","Fry"])
abbList.append(["Field","Fld"])
abbList.append(["Fields","Flds"])
abbList.append(["Flat","Flt"])
abbList.append(["Flats","Flts"])
abbList.append(["Ford","Frd"])
abbList.append(["Fords","Frds"])
abbList.append(["Forest","Frst"])
abbList.append(["Forge","Frg"])
abbList.append(["Forges","Frgs"])
abbList.append(["Fork","Frk"])
abbList.append(["Forks","Frks"])
abbList.append(["Fort","Ft"])
abbList.append(["Freeway","Fwy"])
abbList.append(["Gables","Gables"]) #Hennepin Specific
abbList.append(["Garden","Gdn"])
abbList.append(["Gardens","Gdns"])
abbList.append(["Gate","Gate"]) #Hennepin Specific
abbList.append(["Gateway","Gtwy"])
abbList.append(["Glade","Glade"]) #Hennepin Specific
abbList.append(["Glen","Gln"])
abbList.append(["Glens","Glns"])
abbList.append(["Green","Grn"])
abbList.append(["Greens","Grns"])
abbList.append(["Greenway","Greenway"]) #Hennepin Specific
abbList.append(["Grove","Grv"])
abbList.append(["Groves","Grvs"])
abbList.append(["Harbor","Hbr"])
abbList.append(["Harbors","Hbrs"])
abbList.append(["Haven","Hvn"])
abbList.append(["Heights","Hts"])
abbList.append(["Highway","Hwy"])
abbList.append(["Hill","Hl"])
abbList.append(["Hills","Hls"])
abbList.append(["Hollow","Holw"])
abbList.append(["Horn","Horn"]) #Hennepin Specific
abbList.append(["Inlet","Inlt"])
abbList.append(["Island","Is"])
abbList.append(["Islands","Iss"])
abbList.append(["Isle","Isle"])
abbList.append(["Junction","Jct"])
abbList.append(["Junctions","Jcts"])
abbList.append(["Key","Ky"])
abbList.append(["Keys","Kys"])
abbList.append(["Knoll","Knl"])
abbList.append(["Knolls","Knls"])
abbList.append(["Lake","Lk"])
abbList.append(["Lakes","Lks"])
abbList.append(["Land","Land"])
abbList.append(["Landing","Lndg"])
abbList.append(["Lane","Ln"])
abbList.append(["Light","Lgt"])
abbList.append(["Lights","Lgts"])
abbList.append(["Loaf","Lf"])
abbList.append(["Lock","Lck"])
abbList.append(["Locks","Lcks"])
abbList.append(["Lodge","Ldg"])
abbList.append(["Loop","Loop"])
abbList.append(["Mall","Mall"])
abbList.append(["Manor","Mnr"])
abbList.append(["Manors","Mnrs"])
abbList.append(["Meadow","Mdw"])
abbList.append(["Meadows","Mdws"])
abbList.append(["Mews","Mews"])
abbList.append(["Mill","Ml"])
abbList.append(["Mills","Mls"])
abbList.append(["Mission","Msn"])
abbList.append(["Motorway","Mtwy"])
abbList.append(["Mount","Mt"])
abbList.append(["Mountain","Mtn"])
abbList.append(["Mountains","Mtns"])
abbList.append(["Neck","Nck"])
abbList.append(["Orchard","Orch"])
abbList.append(["Oval","Oval"])
abbList.append(["Overpass","Opas"])
abbList.append(["Park","Park"])
abbList.append(["Parks","Park"])
abbList.append(["Parkway","Pkwy"])
abbList.append(["Parkways","Pkwy"])
abbList.append(["Pass","Pass"])
abbList.append(["Passage","Psge"])
abbList.append(["Path","Path"])
abbList.append(["Pike","Pike"])
abbList.append(["Pine","Pne"])
abbList.append(["Pines","Pnes"])
abbList.append(["Place","Pl"])
abbList.append(["Plain","Pln"])
abbList.append(["Plains","Plns"])
abbList.append(["Plaza","Plz"])
abbList.append(["Point","Pt"])
abbList.append(["Points","Pts"])
abbList.append(["Port","Prt"])
abbList.append(["Ports","Prts"])
abbList.append(["Prairie","Pr"])
abbList.append(["Radial","Radl"])
abbList.append(["Railroad","Railroad"]) #Hennepin Specific
abbList.append(["Ramp","Ramp"])
abbList.append(["Ranch","Rnch"])
abbList.append(["Rapid","Rpd"])
abbList.append(["Rapids","Rpds"])
abbList.append(["Rest","Rst"])
abbList.append(["Ridge","Rdg"])
abbList.append(["Ridges","Rdgs"])
abbList.append(["Rise","Rise"]) #Hennepin Specific
abbList.append(["River","Riv"])
abbList.append(["Road","Rd"])
abbList.append(["Roads","Rds"])
abbList.append(["Route","Rte"])
abbList.append(["Row","Row"])
abbList.append(["Rue","Rue"])
abbList.append(["Run","Run"])
abbList.append(["Shoal","Shl"])
abbList.append(["Shoals","Shls"])
abbList.append(["Shore","Shr"])
abbList.append(["Shores","Shrs"])
abbList.append(["Skies","Skies"]) #Hennepin Specific
abbList.append(["Skyway","Skwy"])
abbList.append(["Spring","Spg"])
abbList.append(["Springs","Spgs"])
abbList.append(["Spur","Spur"])
abbList.append(["Spurs","Spur"])
abbList.append(["Square","Sq"])
abbList.append(["Squares","Sqrs"])
abbList.append(["Station","Sta"])
abbList.append(["Stravenue","Stra"])
abbList.append(["Stream","Strm"])
abbList.append(["Street","St"])
abbList.append(["Streets","Sts"])
abbList.append(["Summit","Smt"])
abbList.append(["Terrace","Ter"])
abbList.append(["Throughway","Trwy"])
abbList.append(["Trace","Trce"])
abbList.append(["Track","Trak"])
abbList.append(["Trafficway","Trfy"])
abbList.append(["Trail","Trl"])
abbList.append(["Tunnel","Tunl"])
abbList.append(["Turn","Turn"]) #Hennepin Specific
abbList.append(["Turnpike","Tpke"])
abbList.append(["Underpass","Upas"])
abbList.append(["Union","Un"])
abbList.append(["Unions","Uns"])
abbList.append(["Valley","Vly"])
abbList.append(["Valleys","Vlys"])
abbList.append(["Viaduct","Via"])
abbList.append(["View","Vw"])
abbList.append(["Views","Vws"])
abbList.append(["Village","Vlg"])
abbList.append(["Villages","Vlgs"])
abbList.append(["Ville","Vl"])
abbList.append(["Vista","Vis"])
abbList.append(["Walk","Walk"])
abbList.append(["Walks","Walk"])
abbList.append(["Wall","Wall"])
abbList.append(["Way","Way"])
abbList.append(["Ways","Ways"])
abbList.append(["Well","Wl"])
abbList.append(["Wells","Wls"])

#List of changes for [St_POS_Dir]
posDirList = [["North","N"],["East","E"],["South","S"],["West","W"],["Northeast","NE"],["Northwest","NW"],["Southeast","SE"],["Southwest","SW"]]
preDirList = [["North","N"],["East","E"],["South","S"],["West","W"]]
############################################
## Read Arguments

if (len(sys.argv) > 1):
    inFC = sys.argv[1]

############################################
# General Purpose Functions
def printit(inputString):
    try:
        print(inputString)
        arcpy.AddMessage(str(inputString))
    except:
        pass

def printerror(inputString):
    print (inputString)
    arcpy.AddError(inputString)

def getField(inFeatureClass, inFieldName):
  fieldList = arcpy.ListFields(inFeatureClass)
  for iField in fieldList:
    if iField.name.lower() == inFieldName.lower():
      return iField
  return None

def fieldExists(inFeatureClass, inFieldName):
  return getField(inFeatureClass,inFieldName) <> None

############################################
# Initial QC

def initialQC():
    if (arcpy.Exists(inFC)):
        printit("PASS: Feature Class {} Exists".format(inFC))
    else:
        printerror("ERROR: Feature Class {} Does Not Exist, Cancelling...".format(inFC))
        return False

    for iFld in requiredFieldList:
        if (fieldExists(inFC,iFld)):
            printit("PASS: Feature Class {} Has Field [{}]".format(inFC,iFld))
        else:
            printerror("ERROR: Feature Class {} Does Not Have Field [{}], Cancelling...".format(inFC,iFld))
            return False

    if not (fieldExists(inFC,newFieldName)):
        printit("GOOD: Feature Class {} Does Not Already Have Field [{}]".format(inFC,newFieldName))
        printit(" ADDING Field [{}]".format(newFieldName))
        try:
            arcpy.AddField_management(in_table=inFC, field_name=newFieldName, field_type="TEXT", field_precision="", field_scale="", field_length="100", field_alias="", field_is_nullable="NULLABLE", field_is_required="NON_REQUIRED", field_domain="")
        except:
            printerror("ERROR: Error While Adding Field [{}], Cancelling...".format(newFieldName))
            return False
        if not (fieldExists(inFC,newFieldName)):
            printerror("ERROR: Unable to Add Field [{}], Cancelling...".format(newFieldName))
            return False
    else:
        printerror("ERROR: Feature Class {} Already Has Field [{}], Cancelling...".format(inFC,newFieldName))
        return False

    return True

############################################
# Main

def makeSubstitution(inList,inValue,inFieldName):
    for iAbbreviationPr in inList:
        if (inValue == iAbbreviationPr[0]): #Found a Match
            return iAbbreviationPr[1]
    printit("WARNING: [{}] of {} does not have a value in the abbreviation list! Potential Error...".format(inFieldName,inValue))
    return inValue

def main():
    cursorFieldList = requiredFieldList
    cursorFieldList.append(newFieldName)

    try:
        iUCursor = arcpy.da.UpdateCursor(inFC,cursorFieldList)
        iRowCount = 0
        iRowMax = 1
        for uRow in iUCursor:

            #Just to give user an indicator that progress is being made
            if (iRowCount>iRowMax):
                printit(" {}".format(iRowCount))
                iRowMax *= 10
                iRowCount+=1

            abbreviateConcatenatedName = ""
            iFldIndex = 0
            for iFld in requiredFieldList:


                if (iFld == newFieldName):
                    uRow[iFldIndex] = abbreviateConcatenatedName
                    iUCursor.updateRow(uRow)
                else:
                    iValue = uRow[iFldIndex].strip() #Strip is just a safe-guard


                    if ((iValue != "") and (iValue != None)):
                        if (iFld == "ST_PRE_DIR"):
                            iValue= makeSubstitution(preDirList,iValue,"ST_PRE_DIR")
                        if (iFld == "ST_POS_TYP"):
                            iValue= makeSubstitution(abbList,iValue,"ST_POS_TYPE")
                        if (iFld == "ST_POS_DIR"):
                            iValue = makeSubstitution(posDirList,iValue,"ST_POS_DIR")

                        if (abbreviateConcatenatedName == ""):
                            abbreviateConcatenatedName = iValue
                        else:
                            abbreviateConcatenatedName+=" "+iValue
                iFldIndex += 1

        del iUCursor
    except RuntimeError as e:
        printerror("ERROR: Error {} Occurred, Cancelling...".format(e))
        try:
            del iUCursor
            del uRow
        except:
            return False
    return True


if __name__ == '__main__':
    if (initialQC() == True):
        if (main() == True):
            printit("Done!")

Quick & Dirty arcpy: Batch Splitting Polylines to a Specific Length.

For some odd reason, I wanted to split all the arcs in a polyline feature class to a specific length–if a specific feature was longer than the target length, it would become two or more separate polyline records.

Here is the bare-bones script that copies an existing feature class into a new feature class then processes each record, splitting it into multiple records if the polyline is longer than the user-specified tolerance.  Some cautionary notes:

  • This is Quick & Dirty code–minimal error catching or documentation.
  • I basically tested this against one feature class (the one I wanted to split) once I got it to work, I quit.
  • There is some rounding error–features may be a tad bit off (a few ten-thousandths of a unit).
  • I did not test against multi-part features.
  • The tolerance is the native units of the data–if your data is in meters but you want to split the polylines every mile, enter 1,609.344.

I have included both a toolbox file (.tbx) and python script (.py).  After loading the toolbox, you’ll have to change the Source of the script by right-clicking on it, selecting the Source tab, and then navigating to the .py file.

Here is the code for the Googlebots, but you are better off just downloading it.

import arcpy
import sys, math

def printit(inMessage):
    print inMessage
    arcpy.AddMessage(inMessage)

if len(sys.argv) > 1:
    inFC = sys.argv[1]
    outFC = sys.argv[2]
    alongDistin = sys.argv[3]
    alongDist = float(alongDistin)
else:
    inFC = "C:/temp/asdfasdf.mdb/jkl"
    OutDir = "C:/temp/asdfasdf.mdb"
    outFCName = "jkl2d"
    outFC = OutDir+"/"+outFCName
    alongDist = 1000

if (arcpy.Exists(inFC)):
    print(inFC+" does exist")
else:
    print("Cancelling, "+inFC+" does not exist")
    sys.exit(0)

def distPoint(p1, p2):
    calc1 = p1.X - p2.X
    calc2 = p1.Y - p2.Y

    return math.sqrt((calc1**2)+(calc2**2))

def midpoint(prevpoint,nextpoint,targetDist,totalDist):
    newX = prevpoint.X + ((nextpoint.X - prevpoint.X) * (targetDist/totalDist))
    newY = prevpoint.Y + ((nextpoint.Y - prevpoint.Y) * (targetDist/totalDist))
    return arcpy.Point(newX, newY)

def splitShape(feat,splitDist):
    # Count the number of points in the current multipart feature
    #
    partcount = feat.partCount
    partnum = 0
    # Enter while loop for each part in the feature (if a singlepart feature
    # this will occur only once)
    #
    lineArray = arcpy.Array()

    while partnum < partcount:
        # Print the part number
        #
        #print "Part " + str(partnum) + ":"
        part = feat.getPart(partnum)
        #print part.count

        totalDist = 0

        pnt = part.next()
        pntcount = 0

        prevpoint = None
        shapelist = []

        # Enter while loop for each vertex
        #
        while pnt:

            if not (prevpoint is None):
                thisDist = distPoint(prevpoint,pnt)
                maxAdditionalDist = splitDist - totalDist

                print thisDist, totalDist, maxAdditionalDist

                if (totalDist+thisDist)> splitDist:
                    while(totalDist+thisDist) > splitDist:
                        maxAdditionalDist = splitDist - totalDist
                        #print thisDist, totalDist, maxAdditionalDist
                        newpoint = midpoint(prevpoint,pnt,maxAdditionalDist,thisDist)
                        lineArray.add(newpoint)
                        shapelist.append(lineArray)

                        lineArray = arcpy.Array()
                        lineArray.add(newpoint)
                        prevpoint = newpoint
                        thisDist = distPoint(prevpoint,pnt)
                        totalDist = 0

                    lineArray.add(pnt)
                    totalDist+=thisDist
                else:
                    totalDist+=thisDist
                    lineArray.add(pnt)
                    #shapelist.append(lineArray)
            else:
                lineArray.add(pnt)
                totalDist = 0

            prevpoint = pnt                
            pntcount += 1

            pnt = part.next()

            # If pnt is null, either the part is finished or there is an
            #   interior ring
            #
            if not pnt:
                pnt = part.next()
                if pnt:
                    print "Interior Ring:"
        partnum += 1

    if (lineArray.count > 1):
        shapelist.append(lineArray)

    return shapelist

if arcpy.Exists(outFC):
    arcpy.Delete_management(outFC)

arcpy.Copy_management(inFC,outFC)

#origDesc = arcpy.Describe(inFC)
#sR = origDesc.spatialReference

#revDesc = arcpy.Describe(outFC)
#revDesc.ShapeFieldName

deleterows = arcpy.UpdateCursor(outFC)
for iDRow in deleterows:       
     deleterows.deleteRow(iDRow)

del iDRow
del deleterows

inputRows = arcpy.SearchCursor(inFC)
outputRows = arcpy.InsertCursor(outFC)
fields = arcpy.ListFields(inFC)

numRecords = int(arcpy.GetCount_management(inFC).getOutput(0))
OnePercentThreshold = numRecords // 100

printit(numRecords)

iCounter = 0
iCounter2 = 0

for iInRow in inputRows:
    inGeom = iInRow.shape
    iCounter+=1
    iCounter2+=1    
    if (iCounter2 > (OnePercentThreshold+0)):
        printit("Processing Record "+str(iCounter) + " of "+ str(numRecords))
        iCounter2=0

    if (inGeom.length > alongDist):
        shapeList = splitShape(iInRow.shape,alongDist)

        for itmp in shapeList:
            newRow = outputRows.newRow()
            for ifield in fields:
                if (ifield.editable):
                    newRow.setValue(ifield.name,iInRow.getValue(ifield.name))
            newRow.shape = itmp
            outputRows.insertRow(newRow)
    else:
        outputRows.insertRow(iInRow)

del inputRows
del outputRows

printit("Done!")

Extract Values to Points (Spatial Analyst) Bug

One of the Spatial Analyst tools we often use in ArcGIS is the “Extract Values to Points” tool.  This allows us to take a point file (well locations in our case) and attach a value (elevations) from a raster image (a DEM) to each point.

Today I was running it for the first time against an Image Service we recently published and I received a warning message,”WARNING 000957: Skipping feature(s) because of NULL or EMPTY geometry”.  But the script seemed to run and the final results said “Succeeded” so I thought it was probably fine.  But as I double-checked, I realized the results were wonky.

Turns out that I had two records with Null geometry in my point file of 397 records.  These two records threw the above error but actually had a value in the [Rastervalu] field.  Turns out all 397 records had values.  These two records were consecutive–let’s say the 100th and 101st records in my shapefile.  What happened is record 100 got the value for record 102, record 101 get the value for 103, record 102 (which has valid geometry) had the value for 104.  This pattern, each record having the value for the record 2 place after it, continued until record 396 which had the value for record 397.  Record 397 also had the value for 397.  So the final three records all had the value for the final record.

What I would have expected would be for the two records with Null Geometry to have null values in the [Rastervalu] field and the rest of the records to have the correct values.  Despite the warning, it is very misleading for all the records to end up with a value.

I have a simplified example below.  I made a point shapefile with four records.  The first, third, and fourth  records have valid geometries; the second has Null geometry.  The second record ends up with the value for the third record.  The third record, has the value for the fourth.  The fourth record being the last record, ends up with the last valid value, which was its own.

The results that I would have hoped for would be for the third record to have a Null value.

The way I envision what is occurring behind the scenes is this:  the process makes a list (more of a stack in programming terms) of result values as it processed the points but just assumes that every record will return a value so it does not track which value goes with which shape.

When it reached the two null geometries, it threw an error but continued on.  It did not add a value for these records to the stack of values–when it comes across records with valid geometry but do not intersect the raster it adds a psuedo-null value of (-9999) to the stack.  After it processed all the records it had 395 values in the stack.  It then went, one-by-one through the stack and populated the records in the output shapefile, the first record got the first value in the stack, the second record got the second value, the 100th record got the 100th value (which came from the location of the 102nd record) and so on.  At the end, the final two records received the last valid value.

This final behavior–using the last valid value–corresponds a bit to a behavior we’ve seen with ArcObjects in general.  When iterating through a table, if a field is Null for a specific row, the value from the last non-Null value for that field is often returned.

I’m in the process of submitting a bug to ESRI.  I’m not sure if this existed prior to ArcGIS 10.0 (I’m guessing it did) or if it occurs in other processes (I’m guessing it does).  I did find out that the “Extract Multi Values to Points” works as expected.  I’m guessing it is because unlike the “Extract Values to Points” which creates a new shapefile, this tool appends fields to the existing shapefile and presumably processes records one-by-one without putting the results in a virtual stack.  The “Extract Multi Values to Points” tool also does not throw any warnings.


Launching a Python script with parameters–3 methods.

Since I use python for different tasks, I launch python scripts a variety of ways. Depending on what I am doing, a single script may need to accept parameters from either:

  1. Passed in from an ArcGIS Toolbox Tool.
  2. Re-occurring default value.  Often used in scheduled processes, a nightly backup, for example.
  3. A temporary set of values used in an interactive, debugging session.

What I often do is make the parameter interpretation flexible to meet my needs.  The sample below shows how I do this.  The logic first checks to see if the correct number of parameters were used to launch the script (i.e. if it is called by an Arc Toolbox tool), where the files for the default files exist or if the debug values are valid, including checking the current date against a hard-coded date variable.  Juggling the conditional structure would allow you to prioritize the options differently.

I am also using Tkinter to display an interactive dialog if none of the three conditions are successfully met.

import os.path
import datetime
import shutil
import sys

theEmailText = "nStart: " + str(datetime.datetime.now())

#This example shows three different ways for a script to receive input paramters.
#
# First, if it was run with the necessary number of parameters, as if launched by
# an ArcToolbox tool, it uses those parameters.

if len(sys.argv) == 2:
    wellsShapeFile = sys.argv[0]
    unwellsShapeFile = sys.argv[1]
    theEmailText = theEmailText + "nUsing Parameters Passed In:nn Located Wells File: "+wellsShapeFile+"n Unlocated Wells File: "+unwellsShapeFile
else:
    dateString = datetime.date.today().strftime("%Y%m%d")
    wellsShapeFile = "C:/cwi5_bk/wells/temp/wells_.shp"
    unwellsShapeFile = "C:/cwi5_bk/wells/temp/unloc_wells.shp"

    #Second attempt is if there are default values that should be used.
    #I use this for a process that is run via scheduled Windows Task
    if (os.path.exists(wellsShapeFile)) and (os.path.exists(unwellsShapeFile)):
        theEmailText = theEmailText + "nUsing Automated Date-Based file names:nn Located Wells File: "+wellsShapeFile+"n Unlocated Wells File: "+unwellsShapeFile
    else:
        #The third method is used for debugging/running in the IDE.
        #I put a check condition so this is valid for one day only
        #And then hard-code the temporary paths.
        #
        #Note that you may want to modify the structure of the IF statement
        #used for methods 2 & 3 so that it checks for the manual-override (3rd)
        #method first
        if dateString == '20101213':
            wellsShapeFile = "C:/cwi5_bk/wells/temp/wells.shp"
            unwellsShapeFile = "C:/cwi5_bk/wells/temp/unloc.shp"
            theEmailText = theEmailText + "nUsing Manual Override file names:nn Located Wells File: "+wellsShapeFile+"n Unlocated Wells File: "+unwellsShapeFile
        else:
            theEmailText = theEmailText + "n Manual Override for file names does not meet data filter"

    if (not os.path.exists(wellsShapeFile)) or (not os.path.exists(unwellsShapeFile)):
        from Tkinter import *
        msgbox = Tk()
        msgbox.title('Error')
        Message(msgbox,text="Must either use ArcTool to launch or edit file parameters", bg='royalblue',fg='ivory', relief=GROOVE).pack(padx=10, pady=10)
        msgbox.mainloop()
        print theEmailText
        quit()

print theEmailText