Before session 2
Conditional execution
Watch the videos. Next two videos (part 1 and part 2) tell how Python executes some statements and skips others.
Slides
Text-book: chapter 3 - conditionals
Test
Go to Moodle and take the second test about the video lectures. You can get up to 2 points for the test. You are not limited in time while taking the test. You can spend as much time as you need. You can answer the questions several times. You can take the test several times. The score of the last attempt is credited.
Homework
The deadline for homework is Sunday. Nevertheless, you can start with homework already before the session.
This week we are into if-else and try-except statements. In real world, programs are developed by mixing these constructions (and others that we have not learned yet). For example, you can write a program that asks an input, checks if the input value is valid, and then depending on the input the program chooses what to output.
Example 1
age_as_string = input("How old are you? ")
try:
age = int(age_as_string)
except:
age = -1
if age < 1:
print("This is not a valid age")
elif age < 18:
print("In Estonia, you are considered as a minor")
elif age < 100:
print("You are an adult")
else:
print("Wow, you need a lot of birthday candles!")
Example 2
try:
x = int(input('Enter first number: '))
y = int(input('Enter second number: '))
if x == y:
print('Numbers are equal')
else:
if x < y:
print(x, 'is less than', y)
else:
print(x, 'is greater than', y)
except:
print('Please enter a number')
Exercise 1. Admission to the University of Tartu
Write a program to solve the following problem.
The University of Tartu uses different coefficients to calculate the admission score for each curriculum. A student's application is considered for admission only if the admission score is 66 points or higher. Your task is to write a program that asks the user for the admission score. The program has to output whether the obtained score is enough to be considered for admission to the University of Tartu. Also the program has to check the validity of the entered score: the maximum points for all curricula are 100; a valid score cannot be negative.
Some examples of the program output are shown below:
Enter the number of points: 85 The obtained points are enough to be considered for admission
Enter a number of points: 65 The obtained points are not enough to be considered for admission
Enter a number of points: 115 You cannot obtain so many points
Enter a number of points: -1 You cannot obtain negative points
Exercise 2. Number of days in months
Write a program that asks the user to enter the number of a month. The program has to output the number of days in that month. Also make sure if the user inputs anything ridiculous, the program has to give a corresponding feedback about it. Use try-except.
Test your program with different inputs and make sure the program works correctly. For example: -100, 0, 1, 2, 5, 9, 10, 12, 13, 100, blabla
Here are some examples of the program output.
Enter the number of a month: blabla Please enter a number
Enter the number of a month: 0 The number of a month must be in the range [1-12]
Enter the number of a month: 12 That month has 31 days in it.
Enter the number of a month: 4 That month has 30 days in it.
Optional part
If you can (and it is not very difficult at all) also try to check against the leap year. In that case, the program has to ask the user about the year.
Here are some examples of the program output if the entered number is 2 (February):
Enter the number of a month: 2 Enter a year: 2015 That month has 28 days in it (a common year).
Enter the number of a month: 2 Enter a year: 2000 That month has 29 days in it (a leap year).
Enter the number of a month: 2 Enter a year: 2100 That month has 28 days in it (common year).
Enter the number of a month: 2 Enter a year: 2016 That month has 29 days in it (a leap year).