topic Re: Getting the field name that contains a max value in python in Python Questions

Getting the field name that contains a max value in python

MaraKaminowitz — Wed, 27 Jun 2018 18:17:00 GMT

I am trying to get the name of a field that contains the maximum value across several rows. Getting the maximum number is easy, I would just use max(a, b, c...). But I would like the field name of that is associated with each high value. Example:

F1	F2	F3
2	34	8
19	4	1
3	7	22

So max in python would give me

But what I want is

Any suggestions?

Re: Getting the field name that contains a max value in python

JonathanQuinn — Sat, 11 Dec 2021 22:08:02 GMT

A search cursor reads each column, so you can iterate through the columns to find the largest value:

from arcpy import da

field_names=["F1","F2","F3"]

with arcpy.da.SearchCursor(r"Data",field_names) as cursor:
    #Iterate through records
    for row in cursor:
        #Iterate through columns
        for val in row:
            #If it's the first record, set the maxVal variable to the record
            if row.index(val) == 0:
                maxVal = val
            else:
                if val > maxVal:
                    maxVal = val
           #Or, set it to 0 by default if you know all values are positive
           ##maxVal = 0
           ##if val > maxVal:
           ##    maxVal = val
        #Then, use indexing to get the field names
        print(field_names[row.index(maxVal)])‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Getting the field name that contains a max value in python

JoshuaBixby — Sat, 11 Dec 2021 22:08:05 GMT

This approach can be simplified a bit:

import arcpy

tbl = # path to table or feature class
flds = ["F1", "F2", "F3"]

with arcpy.da.SearchCursor(tbl, flds) as cur:
    for row in cur:
        print(cur.fields[row.index(max(row))])‍‍‍‍‍‍‍‍

Re: Getting the field name that contains a max value in python

DanPatterson_Retired — Sat, 11 Dec 2021 22:08:08 GMT

For the field calculator

def find_max(flds, names=None):
    """puthon parser
    flds - a list of fields [!a!, !b!, !c!]
    names - a list of field names [a, b, c] 
    in_ = [a, b, c]
    useage : find_max([!a!, !b!, !c!], [a, b, c])
    """
    if (flds is None) or (names is None):
        return None
    else:
        return names[flds.index(max(flds))]
    



find_max([!a!, !b!, !c!], [a, b, c])

# ---- assume [9, 2, 13] for [!a!, !b!, !c!] for example

'c'
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Getting the field name that contains a max value in python

MaraKaminowitz — Mon, 02 Jul 2018 15:11:21 GMT

Thanks. I have a large number of fields. Adding them all into the script isn't hard but for education's sake, is there a way to read them into a single variable? I tried incorporating another for loop to iterate through the field names and feed that into the search cursor, but I just created a mess. I started with

field_names = arcpy.ListFields(featureclass, 'Sum_*')

Re: Getting the field name that contains a max value in python

JoshuaBixby — Mon, 02 Jul 2018 15:40:07 GMT

You are on the right track. ListFields—Help | ArcGIS Desktop doesn't return a list of names, it returns a list of field objects, which you need to extract the names from the objects:

field_names = [fld.name for fld in arcpy.ListFields(featureclass, 'Sum_*')]‍

Re: Getting the field name that contains a max value in python

DanPatterson_Retired — Mon, 02 Jul 2018 15:40:18 GMT

Mara

ListFields returns field objects not their names...

So you could do this

field_names = [f.name for f in arcpy.ListFields(featureclass, 'Sum_')]‍

Re: Getting the field name that contains a max value in python

DanPatterson_Retired — Mon, 02 Jul 2018 15:52:27 GMT

Forgot the * in the wildcard... as in Joshua's...