topic Re: Convert expression in Calculate Field from VB to PYTHON3 in Python Questions

Convert expression in Calculate Field from VB to PYTHON3

SoratoSouza_e_Silva — Wed, 24 Nov 2021 18:18:58 GMT

Hi,

I'm having trouble converting this tool's expression to Python 3, could someone help me?

arcpy.CalculateField_management("selecionado_View", "selecionado_" + Safra + ".SELECIONADO", "[selecionado_" + Safra + ".SELECAO] + [selecionado_" + Safra2 + ".SELECAO]", "VB", "")

I'm not sure what this dot means.

Thank´s

Re: Convert expression in Calculate Field from VB to PYTHON3

MichaelVolz — Wed, 24 Nov 2021 18:41:43 GMT

Do you have the ability to generate this query in Pro SelectbyAttribute interface using python selection and then review the SQL query itself with the toggle?

Re: Convert expression in Calculate Field from VB to PYTHON3

SoratoSouza_e_Silva — Wed, 24 Nov 2021 18:50:54 GMT

more less I can´t simulate this field:

selecionado_" + Safra + ".SELECIONADO", "[selecionado_" + Safra + ".SELECAO]

Re: Convert expression in Calculate Field from VB to PYTHON3

MichaelVolz — Wed, 24 Nov 2021 18:53:52 GMT

This looks like a field concatenation process. Can you list the field names and the data type next to it?

Re: Convert expression in Calculate Field from VB to PYTHON3

SoratoSouza_e_Silva — Wed, 24 Nov 2021 19:25:19 GMT

Safra = Text

Safra2 = Text

SELECAO = Text

"selecionado_" just string to concatenate

Thank´s

Re: Convert expression in Calculate Field from VB to PYTHON3

DanPatterson — Wed, 24 Nov 2021 19:41:16 GMT

From the links I sent earlier, in Python field names are enclosed in exclamation marks

eg Safra !Safra!

Re: Convert expression in Calculate Field from VB to PYTHON3

SoratoSouza_e_Silva — Wed, 24 Nov 2021 19:45:28 GMT

Yes correct but I have problem after of the concatenate: selecionado_" + Safra, Safra = 2122 (Text)

NameError: name 'selecionado_2122' is not defined

Re: Convert expression in Calculate Field from VB to PYTHON3

MichaelVolz — Wed, 24 Nov 2021 19:45:45 GMT

Performing this exercise in Pro itself, as opposed to just adding it to a script, would be helpful to you to learn the syntax that is required per Dan's replies.

Re: Convert expression in Calculate Field from VB to PYTHON3

curtvprice — Wed, 24 Nov 2021 20:16:16 GMT

@SoratoSouza_e_Silva wrote:
Hi,
I'm having trouble converting this tool's expression to Python 3, could someone help me?
arcpy.CalculateField_management("selecionado_View", "selecionado_" + Safra + ".SELECIONADO", "[selecionado_" + Safra + ".SELECAO] + [selecionado_" + Safra2 + ".SELECAO]", "VB", "")
I'm not sure what this dot means

What the dot means, from the help for Add Join:
In the resulting input table, fields will be prefixed with the input's name and a period (.), and all fields from the join table will be prefixed with the join table name and a period as the default.

Here's a crack at a Python 3 conversion. I second the suggestion in this thread that playing around with the Calculate Field tool interactively would help you learn some of the ins and outs of this, especially if you try Copy as Python command after filling out the tool dialog. A key thing to keep in mind is the python string should be directly interpretable as a Python expression (with the exception of field names surrounded by ! characters) and data types are not converted for you as in VB.

# I am assuming Safra, Safra2 are Python variables of type string. tbl = "selecionado_" + Safra # ex. selecionado_foo tbl2 = "selecionado_" + Safra2 # ex. selecionado_foo2 # expr below becomes: # "!selecionado_foo.SELECAO! + !selecionado_foo2.SELECAO!" expr = "!{}.SELECAO! + !{}.SELECAO!".format(tbl, tbl2) arcpy.CalculateField_management("selecionado_View", tbl + ".SELECIONADO", expr, "PYTHON")

Re: Convert expression in Calculate Field from VB to PYTHON3

SoratoSouza_e_Silva — Thu, 25 Nov 2021 18:49:47 GMT

Very good! Thank´s @curtvprice help a lot!