topic Re: CalculateField_management. NameError: name is not defined in Python Questions

CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 03:15:46 GMT

Hello,

Why am I getting a NameError here?

Here is the basic python:

table = r'D:\output.gdb\table'
m = 0.01
arcpy.CalculateField_management(table, 'FIELD_B', '!FIELD_A! * m', 'PYTHON')

The error states: NameError: name 'm' is not defined

How is this so, as I have just defined m right above?

Thanks much for your help!

Best regards, Mike

Re: CalculateField_management. NameError: name is not defined

DanPatterson_Retired — Fri, 12 May 2017 03:57:40 GMT

not sure but try ... '!FIELD_A!' * m

and change to PYTHON_9.3

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 04:05:25 GMT

Thanks for your response.

If I try:

arcpy.CalculateField_management(table, 'FIELD_B', '!FIELD_A! ' * m, 'PYTHON 9.3')

The error is different. It states:

"can't multiply sequence by non-int type of float"

Re: CalculateField_management. NameError: name is not defined

DanPatterson_Retired — Fri, 12 May 2017 04:11:28 GMT

so the multiply by m doesn't work because it is interpreting '!MEAN!' as a string which you can't multiply by a float.

The only other thing I can think of is to put the expression out separately.

m = 0.01

expr = '!MEAN! * {}'.format(m)

which prints out

'!MEAN! * 0.1'

then .... (fltable, field='THRESHOLD', expression=expr, 'PYTHON_9.3')

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 04:19:24 GMT

Thanks Dan. I tried that earlier!

The result is: "SyntaxError: non-keyword arg after keyword arg"

Re: CalculateField_management. NameError: name is not defined

RebeccaStrauch__GISP — Fri, 12 May 2017 08:53:36 GMT

I don't know if thus will make a difference, and not head a machine where I can test, but all the samples show double quote not single around the field and expression.

Calculate Field—Help | ArcGIS Desktop

Re: CalculateField_management. NameError: name is not defined

JoshuaBixby — Sat, 11 Dec 2021 10:07:00 GMT

In Python, you can't pass positional arguments after keyword arguments. With Dan's example, try using all positional:

table = r'D:\output.gdb\table'
m = 0.01
expr = '!FIELD_A! * {}'.format(m)
arcpy.CalculateField_management(table, 'FIELD_B', expr, 'PYTHON_9.3')‍‍‍‍

or using all keywords once you start using keywords:

table = r'D:\output.gdb\table'
m = 0.01
expr = '!FIELD_A! * {}'.format(m)
arcpy.CalculateField_management(table,
                                field='FIELD_B',
                                expression=expr,
                                expression_type='PYTHON_9.3')‍‍‍‍‍‍‍

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 13:16:43 GMT

Joshua, thank you. However, the error now says: Parameters are not valid.
ERROR 000800: The value is not a member of VB | PYTHON | PYTHON_9.3.
Failed to execute (CalculateField).

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 13:35:37 GMT

Somehow, the variable m is not being passed. CalculateField doesn't seem to know anything about the variable m. So...how to pass it?

Re: CalculateField_management. NameError: name is not defined

JoshuaBixby — Fri, 12 May 2017 13:44:49 GMT

If the examples above from Dan and myself, the variable m is not being passed, the variable it getting converted to a value, 0.01 in this case, before being passed to the field calculator. Does the value of m vary by record?

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Fri, 12 May 2017 14:04:50 GMT

No, it doesn't. However, it is a parameter input by the user.

Re: CalculateField_management. NameError: name is not defined

DanPatterson_Retired — Fri, 12 May 2017 15:02:53 GMT

Then you need to show the show the script where the parameter is getting passed. And it is probably a string parameter, so check to see if you need to 'float' it

Re: CalculateField_management. NameError: name is not defined

curtvprice — Sat, 13 May 2017 00:22:57 GMT

This error means you got your parameters out of order. Joshua's first example should work well if you can figure out how to plug in your workflow. Feel free to post a code snippet (formatted, please): https://community.esri.com/people/curtvprice/blog/2014/09/25/posting-code-blocks-in-the-new-geonet?sr=search&searchId=13be51da-da2d-42e6-b339-722a3c2a9a2c&searchIndex=0‌

Re: CalculateField_management. NameError: name is not defined

curtvprice — Sat, 13 May 2017 00:24:24 GMT

No need to float it, a parameter "{}".format("0.1") is the same as "{}".format(0.1). The tricky part is to get your user-input variable into the string m.

Re: CalculateField_management. NameError: name is not defined

DanPatterson_Retired — Sat, 13 May 2017 00:46:28 GMT

.... show the show the script where the parameter is getting passed .... my comment

This is the part that is missing... getparameterastext? getparameter? if it was just 0.01, then everything should work as designed

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Mon, 15 May 2017 17:15:49 GMT

Gentlemen, thanks for your feedback. Been offline couple of days.

Here are the relevant lines of the "real" script in question

slope = arcpy.GetParameterAsText(2)
m = float(slope)
arcpy.CalculateField_management(NHDFlowline,'THRESHOLD', '!MEAN! * m', 'PYTHON')

Where NHDFlowline is an existing table in an output gdb (set as the working environment). A couple fields I have added to this table are THRESHOLD and MEAN.

I am attempting to field calculate THRESHOLD by multiplying (MEAN * m) where m is the slope of a regression line.

Re: CalculateField_management. NameError: name is not defined

DanPatterson_Retired — Sat, 11 Dec 2021 10:07:02 GMT

Here are 4 examples using one of my calculations...

#  formatting the expression
m = 0.1
expr = "!POINT_Y! * {}".format(m)
expr   # yields
'!POINT_Y! * 0.1'


# putting the 0.1 within the expression
arcpy.CalculateField_management(in_table="fishnet_label",
                                field="test",
                                expression="!POINT_Y! * 0.1",
                                expression_type="PYTHON_9.3",
                                code_block="")

# put the expression in from above
arcpy.CalculateField_management(in_table="fishnet_label",
                                field="test",
                                expression=expr,
                                expression_type="PYTHON_9.3",
                                code_block="")

# write a code block
codeblk ='m =  0.1\nglobal m\ndef test(fld):\n    return fld * m')
arcpy.CalculateField_management(in_table="fishnet_label",
                                field="test",
                                expression="test(!POINT_Y!)",
                                expression_type="PYTHON_9.3",
                                code_block=codeblk)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Something has to work

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Sat, 11 Dec 2021 10:07:05 GMT

Thanks for sticking with the thread Dan. I'll go through examples.

NHDFlowline = 'D:\Generalizer\output.gdb\NHDFlowline_0202'
HUC = 'D:\Generalizer\output.gdb\huc12_mn_ppt_0202'
arcpy.CalculateField_management(NHDFlowline,'THRESHOLD','!MEAN! * .01', 'PYTHON')‍‍‍

This first one works. However, m is supposed to be an input parameter so...

m = input("enter m")
NHDFlowline = 'D:\Generalizer\output.gdb\NHDFlowline_0202'
HUC = 'D:\Generalizer\output.gdb\huc12_mn_ppt_0202'
arcpy.CalculateField_management(NHDFlowline,'THRESHOLD','!MEAN! * m', 'PYTHON')‍‍‍‍

This is the usual error I get, which is: NameError: name 'm' is not defined.

Ok, lets use your first example:

m = input("enter m")
expr = '!MEAN!' * {}.format(m)
NHDFlowline = 'D:\Generalizer\output.gdb\NHDFlowline_0202'
HUC = 'D:\Generalizer\output.gdb\huc12_mn_ppt_0202'
arcpy.CalculateField_management(NHDFlowline,'THRESHOLD','expr', 'PYTHON')‍‍‍‍‍

Now the error says:

expr = '!MEAN!' * {}.format(m)
AttributeError: 'dict' object has no attribute 'format'

It thinks that !MEAN! is a dictionary object...

m = input("enter m")
expr = '!MEAN!' * {}.format(m)
NHDFlowline = 'D:\Generalizer\output.gdb\NHDFlowline_0202'
HUC = 'D:\Generalizer\output.gdb\huc12_mn_ppt_0202'
arcpy.CalculateField_management(in_table=NHDFlowline,field='THRESHOLD',expression='expr',expression_type='PYTHON',code_block="")‍‍‍‍‍

This one has the same error: expr = '!MEAN!' * {}.format(m)
AttributeError: 'dict' object has no attribute 'format'

Re: CalculateField_management. NameError: name is not defined

curtvprice — Sat, 11 Dec 2021 10:07:08 GMT

Code block #3 would have worked -- but you need a quote moved, and don't quote expr! (It's a python variable of type str, not a string literal.)

m = input("enter m")
expr = '!MEAN! * {}'.format(m)  # quote entire expression
# if m is .01, expr now is: "!MEAN! * .01"
NHDFlowline = 'D:\Generalizer\output.gdb\NHDFlowline_0202'
HUC = 'D:\Generalizer\output.gdb\huc12_mn_ppt_0202'
arcpy.CalculateField_management(NHDFlowline, 'THRESHOLD', expr, 'PYTHON')‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: CalculateField_management. NameError: name is not defined

MichaelTinker — Mon, 15 May 2017 23:59:16 GMT

Thanks Curtis, that did it!