# % (Modulo) operator

Available with Spatial Analyst license.

Available with Image Analyst license.

## Summary

Finds the remainder (modulo) of the first raster when divided by the second raster on a cell-by-cell basis.

## Discussion

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

When there are multiple operators in an expression, the operators are not necessarily run in left-to-right order. The operator with the highest precedence value will be run first. For more information, see the operator precedence table in Work with operators in map algebra. Use parentheses to control the run order.

The order of the input is relevant for this operator.

Any value modulated (divided) by zero is assigned NoData on the output; therefore, any location on the second input that is zero or NoData will return NoData for that location on the output.

The modulo operator assumes both its inputs are integers. If any inputs are not integer, those inputs will be converted to integers through truncation. Output values are always integers.

Another way to perform the modulo operator is a %= b, which is an alternative way to write a = a % b.

If both inputs are single-band rasters, or one of the inputs is a constant, the output will be a single-band raster.

If both inputs are multiband rasters, the operator will perform the operation on each band from one input, and the output will be a multiband raster. The number of bands in each multiband input must be the same.

If one of the inputs is a multiband raster and the other input is a constant, the operator will perform the operation against the constant value for each band in the multiband input, and the output will be a multiband raster.

If both inputs are multidimensional rasters with the same number of variables, the operator will perform the operation for all slices with the same dimension value, and the output will be a multidimensional raster. The variables in the inputs must have the same dimensions or a common dimension but no uncommon dimensions.

If both inputs have one variable but different names, set the Match Multidimensional Variable environment to False to perform the operation.

If one of the inputs is a multidimensional raster and the other input is a constant, the operator will perform the operation for all slices for all variables against the constant value, and the output will be a multidimensional raster.

## Parameters

 Operand Explanation Data Type in_raster_or_constant1 The numerator input.If the first input is a raster and the second is a scalar, an output raster is created with the remainder being calculated for each input raster value after being divided by the scalar value. Raster Layer | Constant in_raster_or_constant2 The denominator input.If the first input is a scalar and the second is a raster, an output raster is created with the remainder being calculated for each input raster value after being divided into the scalar value. Raster Layer | Constant

## Code sample

% (Modulo) example 1 (Python window)

This sample returns the value of the remainder (modulus) of dividing the cells in the first raster by the second.

``````import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outMod = Raster("degs") % Raster("negs")
outMod.save("C:/sapyexamples/output/outmod.tif")``````
% (Modulo) example 2 (stand-alone script)

This sample returns the value of the remainder (modulus) of dividing the cells in the first raster by the second.

``````# Name: Op_Mod_Ex_02.py
# Description: Finds the remainder of the first raster when divided by
#              the second raster 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("degs")
inRaster2 = Raster("negs")

# Execute Mod
outMod = inRaster1 % inRaster2

# Save the output
outMod.save("C:/sapyexamples/output/outmod")``````