Conditions we can Program With…

1. Conditions we can Program With… Dr. Paige H. Meeker

2. Conditionals If it’s raining, use an umbrella. If a<b, c=10. Otherwise, d=20. If the dog barks, let it outside. If the tub is full, turn off the water. • Execute statements when Boolean expression is true

3. Boolean Expressions 1 + 1 == 2 “CS1301” == “CS1301” 4 < 6 “A” < “L” “A” <= “L” 5.0 != 6.0 • Evaluate to True or False • Comparison and Equality Operations • == Equals • != Not equal • < Less than • > Greater than • <= Less than or equal to • >= Greater than or equal to

4. Logical Operators • Evaluate to True or False • Combine Other Boolean Values • And - both must be true • Or - either evaluates to true • Not - inverts the truth value

5. What do the following evaluate to? (True and True) evaluates to ???? (True and (3 == 2)) evaluates to ??? (False and False) evaluates to ??? (True or True) evaluates to ??? (True or False) evaluates to ??? ((‘a’ > ‘z’) or False) evaluates to ??? not True evaluates to ??? not False evaluates to ??? not (3 < 2) evaluates to ???

6. What do the following evaluate to? (True and True) evaluates to True (True and (3 == 2)) evaluates to False (False and False) evaluates to False (True or True) evaluates to True (True or False) evaluates to True ((‘a’ > ‘z’) or False) evaluates to False not True evaluates to False not False evaluates to True not (3 < 2) evaluates to True

7. Conditionals • Execute statements when expression is true • Boolean expressions • “If” keyword • Group of statements is called a block if (getBattery() < 6): print “Battery Low” x = 23 if (x != 0): print “Nonzero Number” x = 23 if (x > 0 or x < 0): print “Nonzero Number” password = “robots” v = raw_input(“Enter password”) if (v == password): print “permission granted Indent

8. Otherwise … • Execute a block statements when expression is true another block when false • “else” keyword if (getBattery() < 6): print “Battery Low” else: print “Battery OK” x = int(raw_input(“number: “)) if (x != 0): print “Nonzero Number” else: print “Zero!” Indent

9. 2 Note Flute def flute(): if(getLight(“left”) > getLight(“right”)): beep(1, 440) #a4 else: beep(1, 494)#b4 • 2 note flute • Play A when holding left light sensor • Play B when holding right light sensor • Higher values mean less light

10. Nested Conditionals • “If” statements can be nested • Treated like any other statement • getBattery() 3? • getBattery() 5? • getBattery() 4? • getBattery() 7? • getBattery() 6? if (getBattery() < 6): print “Battery Low” if (getBattery() > 4): print “Not too Low”

11. Nested Conditionals • “If” statements can be nested • If/else indentation must match! if (getBattery() < 6): print “Battery Low” if (getBattery() > 4): print “Not too Low” else: print “VERY Low” else: print “Battery OK CS1301 - O'Hara

12. String Matching weather = raw_input(“What’s the weather like?“) if (weather == “rain”): print “Grab your Umbrella” if (weather == “sunny”): print “Grab your shades” print “Don’t forget the suntan lotion” if (weather == “snow”): print “Wow! In SC??” print “GDH – Hide the trays!” • Can’t be all those names at the same time • redundant • What if we want a “catch-all” else • where should it go?

13. Chained Conditionals weather = raw_input(“What’s the weather like?“) if (weather == “rain”): print “Grab your Umbrella” else: if (weather == “sunny”): print “Grab your shades” print “Don’t forget the suntan loation” else: if (weather == “snow”): print “Wow! In SC??” print “GDH – Hide the trays!” else: print “Blink and it will change.” • Mutually exclusive conditions • Just one conditinal to be true

14. Chained Conditionals Shortcut • Only one block will be executed weather = raw_input(“What’s the weather like?“) if (weather == “rain”): print “Grab your Umbrella” elif (weather == “sunny”): print “Grab your shades” print “Don’t forget the suntan lotion” elif (weather == “snow”): print “Wow! In SC??” print “GDH – Hide the trays!” else: print “Blink and it will change.”

15. Chained Conditionals Short-er-cut • Only one block will be executed • Use “or” logical operation Weather = raw_input(“What’s the weather like?“) if (weather == “rain”): print “Grab your umbrella” elif (weather == “icy” or weather == “snow”): print “Watch out!” else: print “Blink and it will change!”

16. Checking the Robots Vitals if (getBattery() > 6.8): print “I’m good as new” if (getBattery() > 6.0): print “I’m healthy” if (getBattery() > 5.0): print “On my way out” else: print “Dead robot walking” • Under what condition does each statement print?

17. Checking the Robot’s Vitals (Again) if (getBattery() > 6.8): print “I’m good as new” elif (getBattery() > 6.0): print “I’m healthy” elif (getBattery() > 5.0): print “On my way out” else: print “Dead robot walking” What’s the difference between this code and the code on the last slide?

18. 3 Note Flute def flute (): l = getLight(“left”) c = getLight(“center”) r = getLight(“right”) if (l > r and l > c): beep(1, 440) #a4 elif (c > l and c > r): beep(1, 494) #b4 else: beep(1, 523) #c4 • 3 note flute • Uses chained conditionals • 3 mutually exclusive events CS1301 - O'Hara

19. Things to try… • Create a function that accepts user input of a number. • If the number is less than 10, move the robot forward for that number of seconds. • If the number is greater than 10, move the robot backward for 5 seconds • If the number is equal to 10, turn the robot for 10 seconds. • Email your functions to me before Wednesday.