Functions … return values

1. Functions … return values # sample code def gross_pay (pay_per_hour, hours_worked): pay = pay_per_hour * hours_worked line of code pretax_pay = gross_pay(10.50, 10.0) print (pretax_pay) What if line of code is: What is returned?Type? return pay return is empty,i.e. no return

2. Variable Scope …where do your names live? • variable scope – where the variable is created, changed, or accessed • when we only had a main program, • there was only one namespace • all variable were in that one namespace • when we create a function, • the function has its own namespace • variable assigned in the function can only be seen by the code in that function

3. Variable Scope …where do your names live? def cube (x):      value = x * x * x      return value value = 25 cubed = cube(2) print (cubed, value)

4. Variable Scope …where do your names live? def clear_count(count): count = 0 return order_num = 15 clear_count(order_num) print(order_num)

5. Variable Scope …where do your names live? def clear_count(count): count = 0 return count = 15 clear_count(count) print(count)

6. Variable Scope …where do your names live? topping = "whipped cream“ def order_ice_cream(flavour): topping = flavour return order_ice_cream("chocolate") print (topping)

7. Variable Scope …where do your names live? topping = "whipped cream“ def order_ice_cream(flavour): print("Mmm,", flavour, "with", topping) return order_ice_cream("chocolate")

8. Variable Scope …where do your names live? If main and functions in same file: If main and functions in different files: variable inside function is local to the function variables inside the main are not visible to the functions separate files make good fences (enforces no peeking) • variable inside function is local to the function • variables inside the main are visible to the functions • be a good neighbour, do not peek.

9. Calculate area and volume of cylinder [A3, Q1] PI = 3.1416 radius = float(input(“Enter cylinder radius: “)) height = float(input(“Enter cylinder height: “)) area = PI * radius**2 volume = area * height print(“Cylinder area = {:.2f}”.format(area)) print(“Cylinder volume = {:.2f}”.format(volume))

10. PI = 3.1416 radius = float(input(“Enter cylinder radius: “)) height = float(input(“Enter cylinder height: “)) print(“Cylinder area = {:.2f}”.format(area)) print(“Cylinder volume = {:.2f}”.format(volume))

11. Lumens given bulb wattage [A6, Q1] • watts = int(input(“Enter watts: “)) • if watts == 15: • lumens = 125 • elif watts == 25: • lumens = 215 • elif watts == 40: • lumens = 500 • elif watts == 60: • lumens = 880 • elif watts == 75: • lumens = 1000 • elif watts == 100: • lumens = 1675 • else: • lumens = None • print() • if lumens == None: • print(“Invalid wattage”) • else: • print(“For a bulb wattage of {} watts, brightness is {} lumens” .format(watts, lumens))

12. Lumens given bulb wattage [A6, Q1] • if watts == 15: • lumens = 125 • elif watts == 25: • lumens = 215 • elif watts == 40: • lumens = 500 • elif watts == 60: • lumens = 880 • elif watts == 75: • lumens = 1000 • elif watts == 100: • lumens = 1675 • else: • lumens = None • watts = int(input(“Enter watts: “)) • print() • if lumens == None: • print(“Invalid wattage”) • else: • print(“For a bulb wattage of {} watts, brightness is {} lumens” .format(watts, lumens))