Choosing which statements to execute

4.4. Choosing which statements to execute#

if some condition is True:
    do something
elif some other condition is True: # else if 
    do something
elif some other condition is True: # else if 
    do something
elif some other condition is True: # else if 
    do something
else:
    do something

  • colons are important and indentation matters

  • can have many elif tests

  • do not need else

  • conditions can be nested

4.4.1. Examples#

pH Level

Solution Category

0-4

Strong acid

5-6

Weak acid

7

Neutral

8-9

Weak base

10-14

Strong base

 
ph = float(input('Enter the pH level: '))
if ph < 7.0:
    print(ph, " is acidic.") #indentation important

ph = float(input('Enter the pH level: '))
if ph < 7.0:
    print(ph, " is acidic.")
    print('You should be careful with that!') #indentation is important

ph = float(input('Enter the pH level: '))
if ph < 7.0:
    print(ph, " is acidic.") #indentation important

if ph > 7.0:
    print(ph, " is basic.") 

ph = float(input('Enter the pH level: '))
if ph < 7.0:
    print(ph, " is acidic.") #indentation important
elif ph > 7.0:
    print(ph, " is basic.") 

ph = float(input('Enter the pH level: '))
if ph < 7.0:
    ph = 8.0 #indentation important
if ph > 7.0:
    print(ph, " is basic.") 

ph = float(input('Enter the pH level: '))
if ph < 7.0:
    ph = 8.0  #indentation important
    print(ph, " is basic.") #
elif ph > 7.0:
    print(ph, " is basic.") 

compound = input('Enter the compound: ')
if compound == 'H2O':
    print('Water')
elif compound == 'NH3':
    print('Ammonia')
elif compound == 'CH4':
    print('Methane')
else:
    print('Unknown compound')

4.4.2. Nested if statements#

value = input('Enter the pH level: ')
if len(value) > 0:
    ph = float(value) 
    if ph < 7.0:
        print(ph, " is acidic.")
    elif ph > 7.0:
        print(ph, " is basic.")
    else:
        print(ph, " is neutral.")

else:
    print('No pH value was given!')

if age < 45:
    if bmi < 22.0:
        risk = 'low'
    else:
        risk = 'medium'
else:
    if bmi < 22.0:
        risk = 'medium'
    else:
        risk = 'high'


young = age < 45
slim = bmi < 22.0
if young:
    if slim:
        risk = 'low'
    else:
        risk = 'medium'
else:
    if slim:
        risk = 'medium'
    else:
        risk = 'high'

young = age < 45
slim = bmi < 22.0
if young and slim:
    risk = 'low'
elif young and not slim :
    risk = 'medium'
elif not young and slim:
    risk = 'medium'
elif not young and not slim:
    risk = 'high'

  • What is wrong with the following code?

ph = 2
if ph < 7.0:
    print(ph, ' is acidic')
elif ph < 3.0:
    print(ph, ' is VERY acidic! Be careful.')

  • Given a number x, print FizzBuzz if it is a multiple of 5 and 7, Fizz if it is a multiple of 5, and Buzz if it is a multiple of 7.

# Implement the min() function for three inputs
def my_min():
    number1 = int(input('Enter first integer: '))
    number2 = int(input('Enter second integer: '))
    number3 = int(input('Enter third integer: '))

    minimum = number1  

    if number2 < minimum:
        minimum = number2

    if number3 < minimum:
        minimum = number3

    print('Minimum value is', minimum)
Contents