Lesson 6 Notes: Home-Made Functions

• What is a function again?
  • Function = defined set of instructions
  • Often stored in sets called modules
  • May or may not take arguments
  • May or may not return values to program
• Function Recipe:
  1. Define the function
  2. Give it a name
  3. Create directions for function to follow
  4. Later in program, call your function
• Setting Up A Function
  
  def name(arguments):
      Commands
  
  • def = required word, lowercase
  • name = You make up
  • (arguments) = initialize variables for function
  • : = Required at end of line
  • Commands = Must be indented to identify it as part of the function.
• Example
  # Define the function
def my_function():
       print “I love school”

#Use function
my_function()
• Program Flow
  • Functions may be defined at any point in the program before the function itself is called.
  • Functions are run when called.
• Feeding Your Function
  • To send values to your functions, create a variable name in the definition
    def my_function(name, name2):
      print name+name2
  • The variable name only works inside the function (it is a local variable)
  • The function can use only local variables.
• Pass the Values, Please
  • To send values to the function, place the values in the function call
    def my_function(name, name2):
      print name+name2
my_function (“Bob”, “White”)
  • Value types must match those expected by the function.
  • Functions can take variables or other functions as arguments.
• Review
  • How do you create a function?
  • How do you send values to a function for processing?
  • What is a “local variable”?
  • Why would reading a program from start to finish not help you understand what happens in the program?