topic Re: Having trouble creating an expression for CalculateField() in Python Questions

Having trouble creating an expression for CalculateField()

GeoDev — Tue, 22 Jun 2021 17:46:36 GMT

arcpy.management.CalculateField(CAD_Anno, "SymbolID", "!SymbolID!.replace('0', '1')", "PYTHON3")

Here is the syntax I wrote and the corresponding Error. I'm decent at python, but I am so confused about how to get this expression working. Basically, in the field of "SymbolID" I want to replace all the 0s with 1s. So the pseudocode would be "If there is a 0 in this current row of the field SymbolID, then replace it with a 1"

Traceback (most recent call last): File "C:/Users/ggroshans/Desktop/append.py", line 14, in <module> arcpy.management.CalculateField(CAD_Anno, "SymbolID", "!SymbolID!.replace('0', '1')", "PYTHON3") File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py", line 5194, in CalculateField raise e File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py", line 5191, in CalculateField retval = convertArcObjectToPythonObject(gp.CalculateField_management(*gp_fixargs((in_table, field, expression, expression_type, code_block, field_type, enforce_domains), True))) File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\_base.py", line 512, in <lambda> return lambda *args: val(*gp_fixargs(args, True)) arcgisscripting.ExecuteError: ERROR 000539: File "<expression>", line 1 0.replace('0', '1') ^ SyntaxError: invalid syntax Failed to execute (CalculateField).

Re: Having trouble creating an expression for CalculateField()

JoshuaBixby — Tue, 22 Jun 2021 18:04:02 GMT

I just tested a similar code snippet in Pro 2.8.0, and everything worked as expected, i.e., no error and expected results. What desktop client and version are you using?

Re: Having trouble creating an expression for CalculateField()

GeoDev — Tue, 22 Jun 2021 18:05:53 GMT

I am also on ArcGIS Pro 2.8.0. Not sure how yours worked and mine is
getting this error message.

Re: Having trouble creating an expression for CalculateField()

JoshuaBixby — Tue, 22 Jun 2021 18:13:24 GMT

How are you executing the code? As a standalone script outside of Pro, a script tool in Pro, the interactive Python window in Pro, Jupyter notebook, etc...?

Re: Having trouble creating an expression for CalculateField()

GeoDev — Tue, 22 Jun 2021 18:15:53 GMT

I'm executing it via standalone script in PyCharm. I have PyCharm connected
to the Python 3.7 (arcgispro-py3) environment.

Re: Having trouble creating an expression for CalculateField()

JayantaPoddar — Tue, 22 Jun 2021 18:20:22 GMT

The issue could be !SymbolID! is a numeric field.

Could you replace

"!SymbolID!.replace('0', '1')"

with

str(!SymbolID!).replace('0','1')

Re: Having trouble creating an expression for CalculateField()

GeoDev — Tue, 22 Jun 2021 18:35:05 GMT

I tried converting it to string and got this error now:

Re: Having trouble creating an expression for CalculateField()

Tomasz_Tarchalski — Tue, 22 Jun 2021 21:39:47 GMT

Hi,

your field is type of Integer or string? if integer, you cannot search and replace strings.

instead of calculcate field, you can also (which is faster by the way) use arcpy.da.UpdateCursor

if your field is integer, you can simply (within cursor) check if your value is equal to 0 or not.

Re: Having trouble creating an expression for CalculateField()

JoshuaBixby — Tue, 22 Jun 2021 21:52:45 GMT

I tried several stand-alone scripts that basically do the same thing your code does, and all of them work as expected.

Given the error message, and the fact I can't reproduce it, make sure you are not copying pasting single and double quotes from other applications because it may be what you think is a single or double quote is not and the Python interpreter is reading your code differently than you expect.