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Getting the field name that contains a max value in python

MaraKaminowitz

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?

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DanPatterson_Retired

Mara

ListFields returns field objects not their names...

So you could do this

field_names <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>f<SPAN class="punctuation token">.</SPAN>name <SPAN class="keyword token">for</SPAN> f <SPAN class="keyword token">in</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>ListFields<SPAN class="punctuation token">(</SPAN>featureclass<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">'Sum_'</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

JoshuaBixby

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 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>fld<SPAN class="punctuation token">.</SPAN>name <SPAN class="keyword token">for</SPAN> fld <SPAN class="keyword token">in</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>ListFields<SPAN class="punctuation token">(</SPAN>featureclass<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">'Sum_*'</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

MaraKaminowitz

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_*')

DanPatterson_Retired

For the field calculator

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">find_max</SPAN><SPAN class="punctuation token">(</SPAN>flds<SPAN class="punctuation token">,</SPAN> names<SPAN class="operator token">=</SPAN>None<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="string token">"""puthon parser
&nbsp;&nbsp;&nbsp; flds - a list of fields [!a!, !b!, !c!]
&nbsp;&nbsp;&nbsp; names - a list of field names [a, b, c] 
&nbsp;&nbsp;&nbsp; in_ = [a, b, c]
&nbsp;&nbsp;&nbsp; useage : find_max([!a!, !b!, !c!], [a, b, c])
&nbsp;&nbsp;&nbsp; """</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN>flds <SPAN class="keyword token">is</SPAN> None<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">or</SPAN> <SPAN class="punctuation token">(</SPAN>names <SPAN class="keyword token">is</SPAN> None<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">return</SPAN> None
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">else</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">return</SPAN> names<SPAN class="punctuation token">[</SPAN>flds<SPAN class="punctuation token">.</SPAN>index<SPAN class="punctuation token">(</SPAN>max<SPAN class="punctuation token">(</SPAN>flds<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN>
&nbsp;&nbsp;&nbsp; 



find_max<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>!a!<SPAN class="punctuation token">,</SPAN> !b!<SPAN class="punctuation token">,</SPAN> !c!<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN>a<SPAN class="punctuation token">,</SPAN> b<SPAN class="punctuation token">,</SPAN> c<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>

<SPAN class="comment token"># ---- assume [9, 2, 13] for [!a!, !b!, !c!] for example</SPAN>

<SPAN class="string token">'c'</SPAN>
<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

JoshuaBixby

This approach can be simplified a bit:

<SPAN class="keyword token">import</SPAN> arcpy

tbl <SPAN class="operator token">=</SPAN> <SPAN class="comment token"># path to table or feature class</SPAN>
flds <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"F1"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"F2"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"F3"</SPAN><SPAN class="punctuation token">]</SPAN>

<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN>tbl<SPAN class="punctuation token">,</SPAN> flds<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cur<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cur<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN>cur<SPAN class="punctuation token">.</SPAN>fields<SPAN class="punctuation token">[</SPAN>row<SPAN class="punctuation token">.</SPAN>index<SPAN class="punctuation token">(</SPAN>max<SPAN class="punctuation token">(</SPAN>row<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

JonathanQuinn

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

<SPAN class="keyword token">from</SPAN> arcpy <SPAN class="keyword token">import</SPAN> da

field_names<SPAN class="operator token">=</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="string token">"F1"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"F2"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"F3"</SPAN><SPAN class="punctuation token">]</SPAN>

<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN>r<SPAN class="string token">"Data"</SPAN><SPAN class="punctuation token">,</SPAN>field_names<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="comment token">#Iterate through records</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">#Iterate through columns</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> val <SPAN class="keyword token">in</SPAN> row<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">#If it's the first record, set the maxVal variable to the record</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">if</SPAN> row<SPAN class="punctuation token">.</SPAN>index<SPAN class="punctuation token">(</SPAN>val<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">==</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; maxVal <SPAN class="operator token">=</SPAN> val
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">else</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">if</SPAN> val <SPAN class="operator token">></SPAN> maxVal<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; maxVal <SPAN class="operator token">=</SPAN> val
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">#Or, set it to 0 by default if you know all values are positive</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">##maxVal = 0</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">##if val > maxVal:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">##&nbsp;&nbsp;&nbsp; maxVal = val</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">#Then, use indexing to get the field names</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN>field_names<SPAN class="punctuation token">[</SPAN>row<SPAN class="punctuation token">.</SPAN>index<SPAN class="punctuation token">(</SPAN>maxVal<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

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