Introduction To Functions

Definition

def say_hello( ):
   print("Hello!")

Arguments

def add_to_two(num):
   print(num+2)
>>> add_to_two(2)
 4

Return

def square(num):
    return num*num
>>> square(6)
36

Shopping List Redux

[function_list.py]:

shopping_list = []

# Prints Instructions
def show_help():
  print("What should we pick up at the store?")
  print("Enter DONE to stop. Enter HELP for this help. Enter SHOW to show items.")

# Adds item to shopping list
def add_to_list(item):
  shopping_list.append(item)
  print("Added! List has {} items.".format( len(shopping_list) ))

# Prints List
def show_list():
  print("Here's your list: ")
  for item in shopping_list:
    print("- " + item)

show_help()

while True:
  new_item = input("> ")
  if new_item == 'DONE':
    break
  elif new_item == 'HELP':
    show_help()
    continue
  elif new_item == 'SHOW':
    show_list()
    continue
  add_to_list(new_item)
  continue

show_list()