CPSC120B - Day 16 Notes

Cool Computer Science Thing of the Day

Quadcopter Acrobatics

Reading Questions

Quiz

quiz 16

Nested Conditionals

Just like with loops, we can put any code we want inside a conditional statment block, including more conditionals

Putting a condition inside of another is equivalent to using the and operator

if x > 0:
    if x < 10:
        print('x is greater than 0 and less than 10)

Chained Conditionals

An else block is executed if the previous if statement is not true
It can not have any condition
An elif, a combination of else and if, is a chimera of an if and an else.

It has a condition like an if, but the condition is only checked if the previous condition was not true

if x < 0:
    print('x is negative')
elif x < 10:
    print('x is not negative but is less than 10')
else:
    print('x is greater than or equal to 10')

Each condition in a chain of elifs is only tested if all of the previous were not true
taking advantage of this, it is sometimes possible to reduce the number of logical operators used

For example, the following more verbose code is functionally equivalent to the above code

if x < 0:
    print('x is negative')
if x > = 0 and x < 10:
    print('x is not negative but is less than 10')
if x >= 10:
    print('x is greater than or equal to 10')

Example - Higher or Lower

Create a game that plays the higher lower guessing game

MIN_NUM = 1
MAX_NUM = 10
NUM_GUESSES = 5
number = random.randrange(MIN_NUM, MAX_NUM)
print("I'm thining a of a number between 1 and 10.")
for i in range(NUM_GUESSES):
    guess = int(input("Enter a number: "))
    if guess < number:
        print("Too low.")
    if guess > number:
        print("Too high.")

Want to add an else statement that applies to both if statements
An else only applies to the one above

Using an elif the else applies to the two above

if guess < number:
    print("Too low.")
elif guess > number:
    print("Too high.")
else:
    print("Got it!")

Also, it keeps asking for input even after correct

Can use nested conditional, to stop it from asking more

if guess == number:
    guess = int(input("Enter a number: "))
    if guess < number:
        print("Too low.")
    elif guess > number:
        print("Too high.")
    else:
        print("Got it!")

Lab

lab16