If Statements

If Statement videos

• Python Tutorial for Beginners 6: Conditionals and Booleans - If, Else, and Elif Statements

  • if/elif/else

  • and, or, not

  • is and id()

  • “Truthy” and “Falsey” Values

Comparison operators

>   # greater than
<   # less than
>=  # greater than or equal to
<=  # less than or equal to
==  # equal to
!=  # not equal to
is  # used to check equality for True, False, and None
in  # determines if something is in a collection

if, else

age = int(input("Please enter your age: "))

if age >= 18:
    print("You can vote")
else:
    print("You can not vote.")

if, elif, else

mark = int(input("Please enter your mark: "))

if mark >= 80:
    print("You have an A")
elif mark >= 70:
    print("You have a B")
else:
    print("You have a C or lower.")

Multiple elif

mark = int(input("Please enter your mark: "))

if mark >= 80:
    print("You have an A")
elif mark >= 70:
    print("You have a B")
elif mark >= 60:
    print("You have a C")
elif mark >= 50:
    print("You have a D")
else:
    print("You FAIL!!!!")

Boolean values in variables

age = 10
old_enough = age > 5

if old_enough is True:
    print("You can ride on the rollercoaster!")

Boolean operators

We need to be able to reproduce these truth tables.

AND

Both inputs need to be True. Think: “Both And”.

A	B	A and B
True	True	True
True	False	False
False	True	False
False	False	False

OR

Either can be True. Think: “Either Or””.

A	B	A or B
True	True	True
True	False	True
False	True	True
False	False	False

NOT

Inverts the Boolean value.

A	not A
True	False
False	True

Boolean operators in if statements

a = 5
b = 7

if a >= 5 and b > 10:  # False
    print("hello")

if a == 5 or b > 100:  # True
    print("goodbye")

if not (a >= 5 and b > 10):  # True
    print("hello")