I want to use the following expression in the arcpy.CalculateField_management tool.

I have a variable called "value" and a field called "Field01"

I want to use (value - Field01) / 20

I can´t seem to find the correct syntax with arcpy.CalculateField_management.

arcpy.CalculateField_management (fc, "test",expression, "PYTHON")

Given error is:

TypeError: cannot concatenate 'str' and 'int' objects

I have tried the following and many other combinations:

expression = value - "!XKoordInt!" / 20

expression = "("+value+"-!XKoordInt!)/20")"

2 Answers 2


Your second listed expression is close:

expression = "({0} - !XKoordInt!)/20".format(value)

Using the format method is generally better than string concatenation, it will take care of different input types and formatting.


Use the format method to put the value into the expression. Using triple quotes will make it easier to have quotes inside the expression, too.

value = 5000
expression = '''({0} - !XKoord!) / 20'''.format(value)

arcpy.CalculateField_management(in_table=fc, field='test',
                                expression=expression, expression_type='PYTHON_9.3')

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