How to Dissolve Polygons Inside a Feature Class Based on Attribute Conditions

Question

I have a large shapefile (saleArea.shp) which includes hundreds of small adjacent polygons. I would like to dissolve the polygons based on some conditions from tValues field into 5 bigger groups like

1-  "tValues" <= 0.151560
2-  "tValues" >= 0.151561 AND "tValues" <= 0.254022
3-  "tValues" >= 0.254023 AND "tValues" <= 0.379095
4-  "tValues" >= 0.379096 AND "tValues" <= 0.540042
5-  "tValues" >= 0.540043 AND "tValues" <= 0.846651

I did this manually by using Select By Attribute for each of the groups then export them as a new shapefile. After that, I used the Dissolve tool on each of the layers and eventually merged all the dissolved layers - which was tedious work (Besides I have more than 50 shapefiles and I must repeat this for all!). Can you please let me now how to do this is by Arcpy?

Update

I tried to do this as PolyGeo commented by using the Python parser

if ("tValues" <= 0.151560):
        return 1
elif ("tValues" >= 0.151561 AND "tValues" <= 0.254022):
        return 2
elif ("tValues" >= 0.254023 AND "tValues" <= 0.379095):
        return 3
elif ("tValues" >= 0.379096 AND "tValues" <= 0.540042):
        return 4
elif ("tValues" >= 0.540043 AND "tValues" <= 0.846651):
        return 5    

but I am getting this error

Answer 1

There is no need to use ArcPy for this.

You can use the Field Calculator with its Python parser and if/elif(x4) to return values of 1 to 5 to a field, perhaps called GROUP.

You can then Dissolve on GROUP to get the five features that you desire.

Answer 2

If anything becomes tedious and repetitive then it's time to get smarter with your processing. You can automate all that you described by using modelbuilder. You drag the tools you used in to modelbuilder, connect them together to create a work flow and then run the model. You'll invest a bit of time creating the model but then you can tweak a parameter and run the whole model again. There are even ways of making the model loop (called iterators). Basically it's time for you to read the Help manual! Go to Desktop > Geoprocessing > Modelbuilder.