[4. Constants, variables, expressions]] Zero basic learning of python, simple and rude

constants, variables, expressions

• The value of constants will not change, such as pi;
• A variable is a quantity whose value can change dynamically;
• Expressions are expressions that perform mathematical or logical operations on constants and variables;
• In Python, we often use one statement to assign values ​​to multiple variables;

      # Define constants, usually all uppercase
      PI = 3.14
  
      # Define a variable whose value can be dynamically changed
      radius = 10
  
      # use expression to assign value to variable area
      area = PI * radius * radius
      print( " The area of ​​the circle before the radius variable is changed is " , area)
  
      # The value of the variable can be dynamically changed
      radius = 20
      area = PI * radius * radius
      print( " The area of ​​the circle after the radius variable is changed is " , area)
  
      # Assign values ​​to multiple variables at the same time
      name, age = "Pythoner", 18
      print(name, age)