topic Re: Using dictionary in field calculator in Python Questions

Using dictionary in field calculator

SSISC_FieldCrew — Thu, 11 Jan 2024 09:21:04 GMT

I am working with the field calculator in ArcPro. I have created a dictionary where the Key is an existing value in a field and the value is the one I would like to replace the existing value with. Below is a portion of my dictionary.

then I have this bit of code where INV_SP_PLA is the field whose data I am trying to replace.

for r in plant_dictionary: if !INV_SP_PLA! in r: !INV_SP_PLA!.replace(r, plant_dictionary[r]) else: pass

ArcPro does not like my dictionary for some reason and I am unsure of what to put in the Expression portion of the field calculator.

Any ideas why this might not be working?

Re: Using dictionary in field calculator

DanPatterson — Thu, 11 Jan 2024 15:43:39 GMT

expression

plant(!INV_SP_PLA!)

code block

def plant(val): """Demo""" plant_dictionary = { "ABUT THE": "Velvet leaf", "ACRO REP": "Russian knapweed", "AEGI CYL": "Jointed goatgrass", "AEGO POD": "Goutweed / bishop's weed", "AILA ALT": "Tree of heaven", "ALHA MAU": "Camel thorn", "ALLI PET": "Garlic mustard" } for r in plant_dictionary: if val in r: val.replace(r, plant_dictionary[r]) return val

Re: Using dictionary in field calculator

SSISC_FieldCrew — Thu, 11 Jan 2024 12:17:18 GMT

Thanks for the prompt reply @DanPatterson. Rather than replace the key "ABUT THE" with the value "Velvet leaf" the code keeps the field values the same.

Re: Using dictionary in field calculator

JoshuaBixby — Thu, 11 Jan 2024 15:25:41 GMT

Are the values exactly the same between the dictionary key and the field in the table? If there is extra text with the value in the field in the table, including any spaces, the match won't happen. Also, does capitalization match? It would help to provide sample data.

Re: Using dictionary in field calculator

DavidWynne — Thu, 11 Jan 2024 22:10:28 GMT

@SSISC_FieldCrew, to start, I would recommend updating a new field, at least until you're sure you have the logic the way you want.

To follow along with what Dan showed, I tried the following:

Expression:

plant(!INV_SP_PLA!)

Code Block:

plant_dictionary = { "ABUT THE": "Velvet leaf", "ACRO REP": "Russian knapweed", "AEGI CYL": "Jointed goatgrass", "AEGO POD": "Goutweed / bishop's weed", "AILA ALT": "Tree of heaven", "ALHA MAU": "Camel thorn", "ALLI PET": "Garlic mustard" } def plant(val): """Demo""" if val in plant_dictionary.keys(): new_val = plant_dictionary[val] return new_val else: return val

Given the below table, the updated values are shown in the `new` field:

I included an `else` condition to return the original value if it's not in the dictionary. Like Joshua mentioned, variations in the original field values would result in some values not being updated.

Re: Using dictionary in field calculator

SSISC_FieldCrew — Fri, 12 Jan 2024 11:57:14 GMT

Yes, the values match exactly and the capitalization also.

Re: Using dictionary in field calculator

SSISC_FieldCrew — Fri, 12 Jan 2024 11:58:57 GMT

Thanks very much @DavidWynne, that did the trick.