Building label expressions

You can use label expressions to adjust the formatting of your labels. In addition to inserting characters and scripting functions, you can use ArcGIS formatting tags in label expressions. These are special characters for changing the appearance of all or part of your labels. For example, you might use the bold formatting tag to make the first line bold in a stacked, multiline label.

Learn more about formatting labels with text formatting tags

A label expression is limited to a single line of code unless you check the Advanced box on the Label Expression dialog box. Checking the Advanced box allows you to enter a function containing programming logic and spanning multiple lines of code.

Field values are automatically cast to text strings. Therefore, if you wish to use a numeric value in an arithmetic operation, or when making a comparison, you will need to cast it back to a numeric data type. The examples below add two integer fields:

Python

int([FIELD1]) + int([FIELD2])

VBScript

cint([FIELD1]) + cint([FIELD2])

JScript

parseInt([FIELD1]) + parseInt([FIELD2])

Steps:

1. Click the Label Manager button on the Labeling toolbar.
2. Click a label class in the Label Classes list.
3. Click the Expression button.
4. Choose a language on the Parser menu.
5. Type a Python, VBScript, or JScript expression. You can also create an expression by double-clicking the field to add it to the expression or by selecting the field and clicking the Append button to append the field to the end of the expression separated by a space.

   Fields are enclosed in square brackets [ ] irrespective of the data type of the layer's data source.

   Optionally, enter ArcGIS text formatting tags in the Expression box to apply formatting to a portion of your label text.

   If your expression will span multiple lines of code, check the Advanced check box and enter your label expression.

6. Click Verify to make sure there are no syntax errors.
7. Click OK on each of the dialog boxes.

Tip:

Both regular and advanced label expressions can be saved as label expression files (.lxp), which can be loaded into other layers or maps.

Expression examples

The following are examples of label expressions:

• Concatenate a string to the value in a field. For example, this expression creates a label where the value of the PARCELNO field is preceded by the text "Parcel no:":
  Python

  "Parcel no: " + [PARCELNO]
  

  VBScript

  "Parcel no: " & [PARCELNO]
  

  JScript

  "Parcel no: " + [PARCELNO]
  

• Round a decimal number to a set number of decimals. For example, this expression displays an Area field rounded to one decimal place:
  Python

  round(float([AREA]), 1)
  

  VBScript

  Round ([AREA], 1)
  

  JScript

  function FindLabel ( [AREA] )
  {
  var ss;
  var num= parseFloat([AREA]);
  ss =  num.toFixed(1);
    return (ss);
  }
  

• Convert your text labels to all uppercase or lowercase. For example, this expression makes a Name field all lowercase:
  Python

  def FindLabel ( [NAME] ):
    S = [NAME]
    S = S.lower()
    return S
  

  VBScript

  LCase ([NAME])
  

  JScript

  [NAME].toLowerCase()
  

• Convert your text labels to proper case. For example, this expression takes a Name field that is in all capitals and makes it proper case:
  Python

  def FindLabel ( [NAME] ):
    S = [NAME]
    S = S.title()
    return S
  

  VBScript

  Function FindLabel ( [NAME] )
  FindLabel = UCase(Left([NAME],1)) & LCase(Right([NAME], Len([NAME]) -1))
  End Function
  

  JScript

  function FindLabel ( [NAME] )
  {
  var str = [NAME];
  var iLen = String(str).length;
  var upper = (str.substring(0,1)).toUpperCase();
  var lower = (str.substring(1, iLen)).toLowerCase()
  return upper + lower;
  }
  

• Create stacked text. For example, this expression creates a label with the Name field and the two address fields all on separate lines:
  Python

  "Name: " + [NAME] + '\n' + [ADDRESS_1] + '\n' + [ADDRESS_2]
  

  VBScript

  "Name: " & [NAME] & vbCrLf& [ADDRESS_1] & vbCrLf& [ADDRESS_2]
  

  JScript

  "Name: " + [NAME] + "\r" + [ADDRESS_1] + "\r" + [ADDRESS_2]
  

• Create stacked text based on text from one field. For example, this expression uses the comma to specify where the stack happens:
  Python

  def FindLabel ( [LABELFIELD] ):
    S = [LABELFIELD]
    S = S.replace(', ', '\n')
    return S
  

  VBScript

  Function FindLabel ( [LABELFIELD] )
  FindLabel = replace([LABELFIELD], ", ", vbnewline)
  End Function
  

  JScript

  function FindLabel ( [LABELFIELD] )
  {
  var r, re;
  var str = [LABELFIELD];
  re = /,/g;
  r = str.replace(re, "\r");
  return r;
  }
  

• Format your labels. For example, this expression displays the label as currency:
  Python

  def FindLabel ( [MAXIMUM_OC], [RATE] ):
    import locale
    locale.setlocale(locale.LC_ALL, '')
    S = locale.currency(float([MAXIMUM_OC]) * float([RATE]))
    return S
  

  VBScript

  "Occupancy Revenue: " & FormatCurrency ([MAXIMUM_OC] * [RATE])
  

  JScript

  function FindLabel ( [MAXIMUM_OC], [RATE] )
  {
  var ss;
  var num1 = parseFloat([MAXIMUM_OC]);
  var num2 = parseFloat([RATE]);
  var num3 = num1 * num2
  ss =  num3.toFixed(2);
    return ("$" + ss);
  }
  

• Specify a conditional if-else statement. These functions label cities with their name in a large, red font if their population is equal to or exceeds 250,000 and in the default label font if the population is less than 250,000:
  Python

  def FindLabel ( [NAME], [POPULATION] ):
    if long([POPULATION]) >= 250000:
      return "<CLR red='255'><FNT size = '14'>" + [NAME] + "</FNT></CLR>"
    else:
      return [NAME]
  

  VBScript

  Function FindLabel ([NAME], [POPULATION])
    if (cLng([POPULATION]) >= 250000) then
     FindLabel = "<CLR red='255'><FNT size = '14'>" + [NAME] + "</FNT></CLR>"
    else
  	 FindLabel = [NAME]
    end if
  End Function
  

  JScript

  function FindLabel ( [NAME], [POPULATION]  )
  {
  if (parseFloat([POPULATION]) >= 250000){
  return ("<CLR red='255'><FNT size = '14'>" + [NAME] + "</FNT></CLR>");
  }
  else
  return ([NAME]);
  }
  

Note:

To label a subset of features based on a field value, create the SQL query in the label class instead of through the label expression.

• Python Language Reference
• Microsoft VBScript Language Reference
• Microsoft JScript Language Reference

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