Hello, I want to select the maximum area of features with the same attribute. If I run the following script I don't get the maximum value of the list. Any ideas why? import arcpy arcpy . env . overwriteOutput = True inFile = r "path... \Default.gdb\NSG_Kreis_Inters" fc = r "path... \Bearbeitung.gdb\data\Test_NSG_Hauptkreis" Fields = [ "OBJECTID_1" , "OBJEKT" , "m2" ] inFileL = "inFileL" arcpy . CopyFeatures_management ( inFile , fc ) arcpy . MakeFeatureLayer_management ( fc , inFileL ) arcpy . AddField_management ( inFileL , "relevant" , "Single" ) arcpy . AddField_management ( inFileL , "m2" , "Long" ) arcpy . CalculateField_management ( inFileL , "m2" , "!Shape_Area!" , "PYTHON_9.3" ) with arcpy . da . SearchCursor ( inFileL , Fields ) as cursor : for row in cursor : sql = "OBJEKT = '{}'" . format ( row [ 1 ] . encode ( 'utf-8' ) ) arcpy . SelectLayerByAttribute_management ( inFileL , where_clause = sql ) myList = list ( ) with arcpy . da . SearchCursor ( inFileL , Fields ) as cursor : for row in cursor : myList . append ( "{}" . format ( row [ 2 ] ) ) print myList print max ( myList ) sql1 = "{} AND m2 = {}" . format ( sql , max ( myList ) ) arcpy . SelectLayerByAttribute_management ( inFileL , "NEW_SELECTION" , where_clause = sql1 ) arcpy . CalculateField_management ( inFileL , "relevant" , 1 , "PYTHON_9.3" ) Here is the result of the prints in lines 31 and 32: ['0', '1012219'] 1012219 ['0', '1012219'] 1012219 ['2', '1344613'] 2 ['2', '1344613'] 2 ['1649705', '2100'] 2100 ['1918769', '2100'] 2100

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maximum of list doesn't work, any ideas why?

JB1234510

Hello,

I want to select the maximum area of features with the same attribute. If I run the following script I don't get the maximum value of the list. Any ideas why?

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

arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>overwriteOutput <SPAN class="operator token">=</SPAN> <SPAN class="token boolean">True</SPAN>

inFile <SPAN class="operator token">=</SPAN> r<SPAN class="string token">"path... \Default.gdb\NSG_Kreis_Inters"</SPAN>
fc <SPAN class="operator token">=</SPAN> r<SPAN class="string token">"path... \Bearbeitung.gdb\data\Test_NSG_Hauptkreis"</SPAN>
Fields <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"OBJECTID_1"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"OBJEKT"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"m2"</SPAN><SPAN class="punctuation token">]</SPAN>

inFileL <SPAN class="operator token">=</SPAN> <SPAN class="string token">"inFileL"</SPAN>

arcpy<SPAN class="punctuation token">.</SPAN>CopyFeatures_management<SPAN class="punctuation token">(</SPAN>inFile<SPAN class="punctuation token">,</SPAN> fc<SPAN class="punctuation token">)</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>MakeFeatureLayer_management<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> inFileL<SPAN class="punctuation token">)</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>AddField_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"relevant"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Single"</SPAN><SPAN class="punctuation token">)</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>AddField_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"m2"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Long"</SPAN><SPAN class="punctuation token">)</SPAN>

arcpy<SPAN class="punctuation token">.</SPAN>CalculateField_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"m2"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"!Shape_Area!"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"PYTHON_9.3"</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>inFileL<SPAN class="punctuation token">,</SPAN> Fields<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>

        sql <SPAN class="operator token">=</SPAN> <SPAN class="string token">"OBJEKT = '{}'"</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>encode<SPAN class="punctuation token">(</SPAN><SPAN class="string token">'utf-8'</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        arcpy<SPAN class="punctuation token">.</SPAN>SelectLayerByAttribute_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> where_clause<SPAN class="operator token">=</SPAN>sql<SPAN class="punctuation token">)</SPAN>

        myList <SPAN class="operator token">=</SPAN> list<SPAN class="punctuation token">(</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>inFileL<SPAN class="punctuation token">,</SPAN> Fields<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
            <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
                
                myList<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"{}"</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
                
        <SPAN class="keyword token">print</SPAN> myList
        <SPAN class="keyword token">print</SPAN> max<SPAN class="punctuation token">(</SPAN>myList<SPAN class="punctuation token">)</SPAN>
                
        sql1 <SPAN class="operator token">=</SPAN> <SPAN class="string token">"{} AND m2 = {}"</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>sql<SPAN class="punctuation token">,</SPAN> max<SPAN class="punctuation token">(</SPAN>myList<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
        
        arcpy<SPAN class="punctuation token">.</SPAN>SelectLayerByAttribute_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"NEW_SELECTION"</SPAN><SPAN class="punctuation token">,</SPAN> where_clause<SPAN class="operator token">=</SPAN>sql1<SPAN class="punctuation token">)</SPAN>
        arcpy<SPAN class="punctuation token">.</SPAN>CalculateField_management<SPAN class="punctuation token">(</SPAN>inFileL<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"relevant"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"PYTHON_9.3"</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>‍</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>

Here is the result of the prints in lines 31 and 32:

['0', '1012219']
1012219
['0', '1012219']
1012219
['2', '1344613']
2
['2', '1344613']
2
['1649705', '2100']
2100
['1918769', '2100']
2100

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Accepted answers

Anonymous User

Hi Johannes Bierer‌,

It looks like the values being returned are all strings which is confusing the issue, as the max() function behaves differently for strings and numbers. What we really want to know is which value is largest once those strings are converted into the integers, so one way you could get around this would be to use a list comprehension to generate a new list with the values converted to integers and run the max function for the new list.

intList <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>int<SPAN class="punctuation token">(</SPAN>value<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">for</SPAN> value <SPAN class="keyword token">in</SPAN> myList<SPAN class="punctuation token">]</SPAN>
max<SPAN class="punctuation token">(</SPAN>intList<SPAN class="punctuation token">)</SPAN>‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

Hope that helps.

Regards,

James

All comments

JoshuaBixby

For the sake of learning, I want to point out that the Python max function takes any iterable. You don't have to rely on creating an intermediate list, you can create a generator expression within the function call directly.

<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> str_list <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'1649705'</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">'2100'</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> 
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> max<SPAN class="punctuation token">(</SPAN>str_list<SPAN class="punctuation token">)</SPAN>
<SPAN class="string token">'2100'</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> 
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> max<SPAN class="punctuation token">(</SPAN>int<SPAN class="punctuation token">(</SPAN>i<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">for</SPAN> i <SPAN class="keyword token">in</SPAN> str_list<SPAN class="punctuation token">)</SPAN>
<SPAN class="number token">1649705</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> <SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

JB1234510

Thank you, that helped a lot.

Anonymous User

Hi Johannes Bierer‌,

intList <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>int<SPAN class="punctuation token">(</SPAN>value<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">for</SPAN> value <SPAN class="keyword token">in</SPAN> myList<SPAN class="punctuation token">]</SPAN>
max<SPAN class="punctuation token">(</SPAN>intList<SPAN class="punctuation token">)</SPAN>‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

Hope that helps.

Regards,

James

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