How can I catch a return Value from “Calculate Value” to start another Tool in ArcGis Model builder?

Question

Hey I have troubles with If/else statements in ArcGis Modelbulider. I have imported TauDEM Toolbox to work with D-infinity algorythm. Since D-Infinity only works with .tif raster files

I wanted to check first if the input raster is an .tif raster. After checking i want to start either D-infinity if the return value is true. If its not i want to convert it.

For that i tried to use the "Calculate Value" Tool with that code

Expression:

check_if_Tiff("%DGM%")

Codeblock:

def check_if_Tiff(DGM):

import arcpy

desc = arcpy.Describe(DGM)

type = desc.format

if type == "TIFF":

return "true"

else:

return "false"

so far so good but i dont know how to catch the return values to use them in another tool. I also dont understand what for is the tool "Merge Branch" cause i only get one return value

I read this documentation https://blogs.esri.com/esri/arcgis/2011/06/06/modelbuilderifthenelse1/ but i cant completely follow it. Do I have to do this with an python script or is there a way

like I am trying?

FreddieGibson · Answer

ModelBuilder doesn't provide a functionality to implement if-then-else logic out of the box. You would have to leverage python to implement this, but there are several approaches you can take. Try taking a look at the following page to see if this may be easier for you to implement.

Using If-Then-Else logic for branching—Help | ArcGIS for Desktop

DanPatterson_Retired · Answer

Rather than going to great lengths to check for all possible things that can go wrong, or provide options as you go, wouldn't it be easier to

* ensure that the output from one section to the other is the required type by setting it as the output default
* if certain requirements are required at the start of the process do the limit checking script there

This might make the flow easier