Clear fields to null with negative number placeholders in ArcGIS

negativeToNull.py

# import modules
import arcpy

# feature class or table to modify
table = r'path/to/featureClass/or/table'

# create update cursor to interate data
with arcpy.da.UpdateCursor(table, '*') as cursor:
  
  # iterate the rows
  for row in cursor:
    
    # value to store the row field index
    i = 0
    
    # for every row field
    while i < len(row):
      
      # if the value in the field is less than zero
      if row[i] < 0:
        
        # set the value to None, or Null
        row[i] = None
        
        # increment the index
        i = i + 1
        
    # update the row
    cursor.updateRow(row)