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arcpy.CalculateField_management - compare: how to return fieldvalues

SilvanStöckli

Hello

I use a python script to compare the value of a field like follows:

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">compare</SPAN><SPAN class="punctuation token">(</SPAN>class1<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>

&nbsp;&nbsp; <SPAN class="keyword token">if</SPAN> class1 <SPAN class="keyword token">in</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="number token">612</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">611</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">return</SPAN> <SPAN class="string token">"Text1"</SPAN>
&nbsp;&nbsp; <SPAN class="keyword token">elif</SPAN> class1 <SPAN class="operator token">==</SPAN> <SPAN class="number token">617</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">return</SPAN> <SPAN class="string token">"Text2"</SPAN>
&nbsp;&nbsp; <SPAN class="keyword token">else</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">return</SPAN> !Field!<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

(followed by arcpy.CalculateField_management....)

this works perfectly to return a standardized text like "Text 1" or "Text 2".

But what I really want to do is I want to return a field-value instead of a text.

If (612, 611) return Field1-value;

if (617) return Field2-value.

I tried it with !Field! instead of "Text 1" but it didn't work.

What's the code to return a fieldvalue instead of text?

Thanks for your help!

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Accepted answers

DanPatterson_Retired

def compare(class1, another_value):

&nbsp;&nbsp; if class1 in (612, 611):
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return "Text1"
&nbsp;&nbsp; elif class1 == 617:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return "Text2"
&nbsp;&nbsp; else:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return another_value

# Expression below

compare(!some_field!, !another_field!)<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>

set scale band tools.png

DougBrowning_0-1732141808442.png

All comments

DanPatterson_Retired

You would have to change !Field1! to class1 since class1 is representing what you find in Field1 and your script as it stands, has no idea what Field1 is.

SilvanStöckli

thanks for your help

the problem ist that I don't want to return the value from the field I'm comparing with but the value from an other field in the same table.

That's why I tried to use !"AnotherFieldName"! with those "!!"

DanPatterson_Retired

def compare(class1, another_value):

&nbsp;&nbsp; if class1 in (612, 611):
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return "Text1"
&nbsp;&nbsp; elif class1 == 617:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return "Text2"
&nbsp;&nbsp; else:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return another_value

# Expression below

compare(!some_field!, !another_field!)<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>

set scale band tools.png

DougBrowning_0-1732141808442.png

SilvanStöckli

I thought I found the solution:

<SPAN class="keyword token">return</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>CalculateField_management<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> field<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"!AnotherFieldName!"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"PYTHON_9.3"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">""</SPAN><SPAN class="punctuation token">)</SPAN>‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

But this calculates new values for the whole table instead of only for the ones with value 612 in "field"

Any idea?

Thanks for your help!

JoshuaBixby

Calculate Field is a set-based tool. If you want to update only a subset of records, you need to either create a feature layer and apply a selection set or embed some logic into the code block.

LukeWebb

Dan posted the solution, ill rewrite it more explicitly for your question. You can pass as many values/fields to a function as you like so that you can then return their values.

def compare(class1, class2, class3):

&nbsp;&nbsp; if class1 in (612, 611):
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return class2
&nbsp;&nbsp; elif class1 == 617:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return class3
&nbsp;&nbsp; else:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return class1

# Expression below

compare(!some_field!, !another_field!, !another_field2!)

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