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Available with Spatial Analyst license.

Available with Image Analyst license.

Summary

Adds (sums) the values of two rasters on a cell-by-cell basis.

Illustration

Plus illustration
OutRas = Raster("InRas1") + Raster("InRas2")

Discussion

When using an operator with a raster input the result will be a raster. However, if all inputs are numbers, then the result is a number.

When multiple operators are used in an expression, they are not necessarily executed in left-to-right order. The operator with the highest precedence value will be executed first. For more information on operator precedence, see operator precedence table. You can use parentheses to control the execution order.

The order of input is irrelevant for this operator.

If both input values are integers, the output values will be integers; otherwise, the output will be floating-point values.

Another way to perform the addition operation is a += b, which is an alternative way to write a = a + b.

Syntax

in_raster_or_constant1 + in_raster_or_constant2
OperandExplanationData Type
in_raster_or_constant1

The input to which values will be added.

If one of the input is a raster and the other is a scalar, an output raster is created with the scalar value being added to each cell in the input raster.

Raster Layer | Constant
in_raster_or_constant2

The input whose values will be added to the first input.

If one of the inputs is a raster and the other is a scalar, an output raster is created with the scalar value being added to each cell in the input raster.

Raster Layer | Constant

Return Value

NameExplanationData Type
out_raster

The output raster object.

The cell values are the sum of the first input added to the second.

Raster

Code sample

+ (Addition) example 1 (Python window)

This sample adds two input rasters.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outPlus = Raster("degs") + Raster("negs")
outPlus.save("C:/sapyexamples/output/outplus.img")
+ (Addition) example 2 (stand-alone script)

This sample adds two input rasters.

# Name: Op_Plus_Ex_02.py
# Description: Adds the values of two rasters on a cell-by-cell basis.
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster1 = Raster("cost")
inRaster2 = Raster("degs")

# Execute Plus
outPlus = inRaster1 + inRaster2

# Save the output 
outPlus.save("C:/sapyexamples/output/outplus")

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