Can anyone explain what I've done wrong here. Have a feeling this is really simple...(new to Python). This code si being pasted into the Immediate window in ArcMap 10.1, in order to calculate a field with an "incrementing" value. I would like to specify the starting value externally. Thanks! This works: arcpy . CalculateField_management ( "xx4_ncard" , "as_drv_srt" , "autoIncrement()" , "PYTHON_9.3" , "rec = 0 \ndef autoIncrement ( ) : \n global rec\n pStart = 1 #adjust start value, if req'd \n pInterval = 1 #adjust interval value, if req'd\n if (rec == 0): \n rec = pStart \n else: \n rec = rec + pInterval \n return rec") This doesn't: start = 1 arcpy . CalculateField_management ( "xx4_ncard" , "as_drv_srt" , "autoIncrement()" , "PYTHON_9.3" , "rec=0\ndef autoIncrement():\n global rec\n pStart = " + start + " #adjust start value, if req'd \n pInterval = 1 #adjust interval value, if req'd\n if (rec == 0): \n rec = pStart \n else: \n rec = rec + pInterval \n return rec")

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including Python variable in codeblock

KeithD1

Can anyone explain what I've done wrong here. Have a feeling this is really simple...(new to Python). This code si being pasted into the Immediate window in ArcMap 10.1, in order to calculate a field with an "incrementing" value. I would like to specify the starting value externally.

Thanks!

This works:

arcpy<SPAN class="punctuation token">.</SPAN>CalculateField_management<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"xx4_ncard"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"as_drv_srt"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"autoIncrement()"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"PYTHON_9.3"</SPAN><SPAN class="punctuation token">,</SPAN>"rec<SPAN class="operator token">=</SPAN><SPAN class="number token">0</SPAN>\ndef autoIncrement<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>\n <SPAN class="keyword token">global</SPAN> rec\n pStart <SPAN class="operator token">=</SPAN> <SPAN class="number token">1</SPAN> <SPAN class="comment token">#adjust start value, if req'd \n pInterval = 1 #adjust interval value, if req'd\n if (rec == 0): \n&nbsp; rec = pStart \n else: \n&nbsp; rec = rec + pInterval \n return rec")</SPAN>
<SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

This doesn't:

start <SPAN class="operator token">=</SPAN> <SPAN class="number token">1</SPAN>

arcpy<SPAN class="punctuation token">.</SPAN>CalculateField_management<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"xx4_ncard"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"as_drv_srt"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"autoIncrement()"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"PYTHON_9.3"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"rec=0\ndef autoIncrement():\n global rec\n pStart = "</SPAN> <SPAN class="operator token">+</SPAN> start <SPAN class="operator token">+</SPAN> " <SPAN class="comment token">#adjust start value, if req'd \n pInterval = 1 #adjust interval value, if req'd\n if (rec == 0): \n&nbsp; rec = pStart \n else: \n&nbsp; rec = rec + pInterval \n return rec")</SPAN>
<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

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Accepted answers

DarrenWiens2

You can't concatenate a string and a number. Convert the number to a string before concatenating: str(start)

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curtvprice

I converted to question (Actions menu, upper right) and gave Darren his deserved cookie.

Keith, I know you're new to Python but have to mention this: the CalculateField tool is great in Desktop and ModelBuilder, but in many cases update cursors are FAR easier for this kind of thing in scripting:

To wit:

val <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN>
inc <SPAN class="operator token">=</SPAN> <SPAN class="number token">1</SPAN>
<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>UpdateCursor<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"xx4_ncard"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"as_drv_srt"</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> rows<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> rows<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="operator token">=</SPAN> val
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; val <SPAN class="operator token">+=</SPAN> inc
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; rows<SPAN class="punctuation token">.</SPAN>updateRow<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>

bixb0012

For future reference, please mark questions as questions, instead of discussions.

KeithD1

Thanks for the quick reply - the code now works as expected.

DarrenWiens2

You can't concatenate a string and a number. Convert the number to a string before concatenating: str(start)

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