—Jan 27, 2021

Complex condition checks¶

Conditional execution can be completed using the if statement.

if syntax

>>> if expression:
        # code to execute
    elif expression:
        # code to execute
    else:
        # code to execute
    ```

Boolean values can be either False or True

Boolean operators

x *or* y - If either x OR y is true, the expression is executed
x *and* y - If x AND y are both true, the expression is executed

Comparison operators

< less than
< greater than
== is equal to
>= greater than or equal to
<= less than or equal to
!= not equal to
x *in* [a,b,c] Does x match the value of a, b, or c

# A student makes honour roll if their average is >=85
# and their lowest grade is not below 70
gpa = float(input('What was your Grade Point Average? '))
lowest_grade = input('What was your lowest grade? ')
lowest_grade = float(lowest_grade)

if gpa >= .85 and lowest_grade >= .70:
		print('You made the honour roll')

Demo: dates¶

# I check to see if the requirements for honour roll are met
gpa = float(input('What was your Grade Point Average? '))
lowest_grade = float(input('What was your lowest grade? '))

# Boolean variables allow you to remember a True/False value
if gpa >= .85 and lowest_grade >= .70:
	honour_roll = True
else:
	honour_roll = False

# Somewhere later in your code if you need to check if students is 
# on honour roll, all I need to do is check the boolean variable
# I set earlier in my code
if honour_roll:
	print('You made honour roll')

PPT Demonstrations¶

Challenges time¶

Check the following script and try to find the mistake:

# When you join a hockey team you get your name on the back of the jersey
# but the jersey may not be big enough to hold all the letters
# Ask the user for their first name

# Ask the user for their last name

# if first name is < 10 characters and last name is < 10 characters 
#       print first and last name on the jersey
# if first name >= 10 characters long and last name is < 10 characters
#       print first initial of first name and the entire last name
# if first name < 10 characters long and last name is >= 10 characters
#       print entire first name and first initial of last name
# if first name >= 10 characters long and last name is >= 10 characters
#       print last name only

# Test with the following values
# first name: Susan  last name: Ibach
# output: Susan Ibach
# first name: Susan  last name: ReallyLongLastName
# output: Susan R.
# first name: ReallyLongFirstName  last name: Ibach
# output: R. Ibach
# first name: ReallyLongFirstName  last name: ReallyLongLastName
# output: ReallyLongLastName

solutions:

# When you join a hockey team you get your name on the back of the jersey
# but the jersey may not be big enough to hold all the letters
# Ask the user for their first name
first_name = input('Please enter your first name: ')
# Ask the user for their last name
last_name = input('Please enter your last name: ')

# if first name is < 10 characters and last name is < 10 characters 
#       print first and last name on the jersey
# if first name >= 10 characters long and last name is < 10 characters
#       print first initial of first name and the entire last name
# if first name < 10 characters long and last name is >= 10 characters
#       print entire first name and first initial of last name
# if first name >= 10 characters long and last name is >= 10 characters
#       print last name only

# Check length of first name
if len(first_name) >=10:
    long_first_name = True
else:
    long_first_name = False

# Check length of last name
if len(last_name) >= 10:
    long_last_name = True
else:
    long_last_name = False
 
# Evaluate possible jersey print combinations for different lengths
if long_first_name and long_last_name:
    print(last_name)
elif long_first_name:
    print(first_name[0:1] + '. ' + last_name)
elif long_last_name:
    print(first_name + ' ' + last_name[0:1] + '.')
else:
    print(first_name + ' ' + last_name)