Conditional Statement

When certain condition met, do something.

Syntax

• if
• if else
• if elif
• if elif else

examples

price = 1000
if price > 1000:
    # block of code executed when condition is truthy
    print('price is more than 1000')

if price > 1000:
    # block of code executed when condition is truthy
    print('price is more than 1000')
else:
    # block of code executed when condition is falsy
    print('price is less than 1000')

Falsy values

• False
• None
• 0, 0.0, 0j (int, float, complex)
• '' (empty string)
• [] (empty list)
• {} (empty dictionary)
• set() (empty set)
• () (empty tuple)
• range(0) (empty range)

Truthy values

everything else is truthy

Multiple conditions

you can use elif to add more conditions as many as you need. The order of the conditions matters when they are overlaping. If no overlaping, order of conditions does not matter.

Non-overlaping conditions

number = -20

if number > 0:
    print('positive')
elif number < 0:
    print('negative')
else:
    print('zero')

Overlaping conditions

Put more specific conditions first then generic conditions.

number = 11

if number % 3 == 0 and number % 5 == 0:
    print('Number is divisible by 3 and 5')
elif number % 3 == 0:
    print('Number is divisible by 3')
elif number % 5 == 0:
    print('Number is divisible by 5')
else:
    print('Number is not divisible by 3 and 5')

Conditions inside function

function to calculate member discount

def calc_discount(price: int, is_member: bool):
    if is_member:
        # if is_member is true, discount is 10%
        return price - price * 0.1
    # otherwise, discount is 5%
    return price - price * 0.05

# call function with keyword arguments and assign to variable
discounted_price = calc_discount(price=1000, is_member=True)
print(discounted_price)
# 900.0

function to calculate German Academic Grade

def get_grade(score: int):
    # 91 - 100
    if score >= 91:
        return 'Sehr Gut'
    # 81 - 90
    if score >= 81:
        return 'Gut'
    # 66 - 80
    if score >= 66:
        return 'befriedigend'
    # 50 - 65
    if score >= 50:
        return 'ausreichend'
    # 0 - 49
    return 'nicht bestanden'

print(get_grade(85))
# 'Gut'