Adding "0" to front of all values in column using ArcGIS Field Calculator

I think How To: Keep leading zeros for zip codes in ArcGIS attribute tables has the information you needed about how to keep leading zeros for zip code field.

Zip codes are exclusively numbers, and are often stored in a numeric (formatted) field. When a zip code with leading zeros is entered in a numeric field, the leading zeros are omitted, therefore creating an incorrect zip code. ArcMap tries to match the data type with the appropriate field types for imported tables, often causing zip codes to be designated to a numeric field.

As Brian mentioned you will need to store the data in a text field. Then the field calculation is: right("00000" + [Existing_ZIP_CODE_FIELD],5)

this will ensure you have all of the necessary leading 0s up to 5 characters.

As @Brian has said, the field will have to be text to keep the zero on the left. Here's a quick, basic python example:

import arcpy

#add path to shapefile, feature class
fc = "..."

arcpy.AddField_management(fc, "ZIP5", "TEXT", "", "", 5)

rows = arcpy.UpdateCursor(fc)
for row in rows:
    #row.ZIP4 should be changed to the field
    #with your ZIP, ex: row.ZIP_CODE
    new_value = str(row.ZIP4)[:5].rjust(5,"0")
    row.ZIP5_2 = new_value
    rows.updateRow(row)
del row
del rows

This makes use of UpdateCursor, Add Field (Data Management), and Python string formatting, particularly .rjust()

use & instead of + for this to work in VBA right("00"& [CID],2)

Using python not the field calc but still works.

Used for dynamically adding leading zeros to a field based on the desired number of leading zeros and the length of the string with basic error handling

For example:

• 2 = 00002
• 89 = 00089
• 187 = 00187
• 2098 = 02098

Note the field must be Text otherwise there is no point into running this.

Run in ArcMap

fc_name = 'NAME'
fields = ["FIELD_NAME"]

desired_length = 5

with arcpy.da.UpdateCursor(fc_name, fields) as cursor:
    for row in cursor:
        if row[0].isdigit():
            if len(row[0]) < desired_length:

                row[0] = row[0].zfill(desired_length)
                print row
                cursor.updateRow(row)

            elif len(row[0]) > desired_length:
                print ("> Lenght - Manually Check: " + row[0])
        else:
            print ("NAN - Manually Check: " + row[0])

print ("Finished")