Specifying input data

All Map Algebra statements require input on which to apply the tools and operators (except for CreateNormalRaster and CreateRandomRaster, which have only optional arguments).

Input rules

• To use input data directly (data on disk, layers, tables, field names), it must be in a quoted string.

  # The full path and nmae of the dataset is used
  outRas = Slope("C:/Data/elevation")
  
  # If the layer is in the Table of contents or in your workspace then just the quoted name is needed
  outRas2 = Slope("elevation")

  # In the following statement Population is a field name
  outRas2 = KernelDensity("inpoints", "Population")   

• Existing input data can be assigned to a variable, and the variable can be used in a statement. Variables are not quoted.

  inputElevation = "C:/Data/dem"
  outRas = slope(inputElevation)

• Raster objects can be used as input into subsequent statements. Since a raster object is a variable, it is not quoted.

  outSource = ExtractByAttributes("inraster", "Value > 3000")
  
  # The output of ExtractByAttributes is used as input to EucDistance
  outDistance = EucDistance(outSource)

• Result objects can also be used as input into Map Algebra expressions.

  # Buffer returns a Result object, which is used here as 
  #   input to EucDistance
  dist = EucDistance(arcpy.Select_analysis("schools", "#", "Pop>2000"))

• Many tools accept multiple inputs for a parameter (multivalue input). Inputs are separated by commas and enclosed in square brackets (denoting a Python list).

  outStats = CellStatistics(["inraster1", "inraster2", "inraster3"], "MEAN")