Arcpy text strings as gp expressions

Question

I’m using a while statement to count down from x until it = y. Each loop decreases x by 1. This variable (among other variables) is passed into a geoprocessing tool’s expression variable as a string. The string exactly mimics a user specified expression. Alas the ArcPy .gp does not accept my identical variable as an expression.

How does one take a text string, and pass it off as a text expression?

####### Raster values to separate rasters
import arcpy
arcpy.CheckOutExtension("spatial")

######## Script arguments

FolderLocation = "C:\\Data\\Testing\\"
InRaster = "C:\\Data\\ basin00_dem"

TopVal = 236
BotVal = 127
Range = TopVal-BotVal
print "There are: "+ str(Range) +" values to iterate"
print " "
SingleValue = "s1_"

MegaCount = TopVal

while (MegaCount) > BotVal:
    MegaCount = MegaCount-1
    ## Reclass Single Values
    SingleValueName = SingleValue + str(MegaCount) +".tif"
    SingleValueNamePath = FolderLocation + SingleValueName
    RC1 = "\"" + str(BotVal) +" "
    RC2 = MegaCount -1
    NODATA = " NODATA;"
    RC3 = str(MegaCount) +" "
    RC4 = str(TopVal)+ " "
    Val = "1 " + "\""
    Qu = "\""
    Equ = str(RC1) +str(RC2) + NODATA + str(RC3) + str(RC4) + str(Val) +str(Qu)
    Range = Range -1
    print "Number: " + str(Range) + " Equ: " +str(Equ)
    arcpy.gp.Reclassify_sa(InRaster, "Value", Equ , SingleValueNamePath, "NODATA")


# WORKING .GP
# arcpy.gp.Reclassify_sa(InRaster, "Value", "127 233 NODATA;234 236 1", SingleValueNamePath, "NODATA")
# Example print of Equ: "127 129 NODATA;130 236 1"

Answer 1

I'm only addressing the "How does one take a text string, and pass it off as a text expression?" part here but try using Python string formatting as below:

RC1 = str(BotVal)
RC2 = str(MegaCount - 1)
NODATA = "NODATA"
RC3 = str(MegaCount)
RC4 = str(TopVal)
Val = "1"
Qu = ""
Equ = "{0} {1} {2}; {3} {4} {5} {6}".format(RC1,RC2,NODATA,RC3,RC4,Val,Qu)
print Equ

Answer 2

I think you'll find your problem is:

arcpy.gp.Reclassify_sa

should be:

arcpy.sa.Reclassify

it goes like this:

Raster = arcpy.sa.Reclassify(InRaster,"Value",Equ, "NODATA")
Raster.save(SingleValueNamePath)

The spatial analyst / raster objects have changed since 9.x.

BTW, there's nothing wrong with your iteration but the pythonic way to do it is:

TopVal = 236
BotVal = 127
ValRange = range(TopVal,BotVal,-1) # creates a list of integers
print "There are: "+ str(len(ValRange)) +" values to iterate"

for MegaCount in ValRange:
    # now step through each value in the range
    # The MegaCount works as normal but don't do MegaCount = MegaCount-1
    SingleValueName = SingleValue + str(MegaCount) +".tif"
    SingleValueNamePath = FolderLocation + SingleValueName
    # and so on...