[3. Identifier]] Zero-based learning python, simple and rude

identifier

• Identifiers are characters used to name constants , variables , methods , classes, and modules ;
• Identifiers can be uppercase and lowercase letters , numbers , and underscores ;
• The name cannot start with a number;
• case sensitive;
• The naming style can be: 
  √ CamelCase 
  √ Lowercase + Underscore 

  # Lowercase letter + underscore style variable definition
  the_radius_1 = 10
  
  # CamelCase variable definitions
  theRadius2 = 10
  
  # Lowercase letter + underscore style method definition
  def get_circle_area_1(r):
      return 3.14 * r * r
  
  # CamelCase method definition
  def getCircleArea2(r):
      return 3.14 * r * r