Lecture 2, Part 1 Exercises

Before starting, please run the following cell

In [ ]:
from __future__ import division, print_function 

Question 1

For what value of x will the following code segment print "yes"? Modify these lines to make this happen.

In [1]:
def printX(x):
    if x == 5:
        print("yes")

printX(1)  # Modify this line to make this happen! e.g. what happens if you try printX(2), printX(3), etc..

Question 2

What do you expect the following calls to print?

2.1

def foo():
    if -10 == 10:
        print('Hello world!')
    else:
        print('Goodbye world!')
foo()
In [ ]:
# Write your answer here!

How can you verify your solution using the code above?

In [2]:
# Write code here to verify! 

2.2

def bar():
    if -10 < 10:
        print('Hello world!')
    else:
        print('Goodbye world!')
bar()
In [ ]:
# Write your answer here!

How can you verify your solution using the code above?

In [3]:
# Write code here to verify! 

2.3

def foobar():
    if -10 != 10:
        print('Hello world!')
    else:
        print('Goodbye world!')
foobar()
In [ ]:
# Write your answer here!

How can you verify your solution using the code above?

In [ ]:
# Write code here to verify! 

Question 3

3.1

For what value of x would this function print "five"? "six"? "other"?

In [ ]:
def printX(x):
    if x == 5:
        print("five")
    elif x == 6:
        print("six")
    else:
        print("other")

printX(1) # Modify this line
# answer "five"
# answer "six"
# answer "other" Note: Are there many ways to get `"other"` or only one way?

Question 4

4.1

We will present incorrect functions that takes an integer test score between 0 and 100 as an input, and prints the corresponding letter grade. You will be asked to fix the errors in the code.

(This process of finding and fixing the errors is called debugging.)

Here are the cutoffs:

90-100   A

80-89    B

70-79    C

60-69    D

0-60     F     

Warmup: Daniel has gotten score 75 on an exam. What letter grade (from A to F) does this correspond to?

In [4]:
# Write your answer from A to F here 

4.2

A student tried to write the code for this. Here is their attempt:

In [23]:
def printGradeIncomplete(x):
    if x >= 90:
        print("A")
    elif x >= 80:
        print("B")
    elif x >= 70:
        print("C")
    elif x >= 60:
        print("D")

This code, however, is incomplete. Can you see why? What happens if a student gets 55? Modify the code above (add an else statement to the printGradeIncomplete function) to take care of this case.

4.3

Another student tries to code a different method. This however, is also incorrect.

In [23]:
def printGradeIncorrect(x):
    if x >= 60:
        print("D")
    elif x >= 70:
        print("C")
    elif x >= 80:
        print("D")
    elif x >= 90:
        print("A")
    else:
        print("F")

Can you spot the error in the code above? For what input scores will this print the right letter?

In [6]:
# Use this box to call the function `printGradeIncorrect(x)` and see what happens.

4.4

Now the student thinks he's got it. This also does not work as expected though.

In [23]:
def printGradeIncorrect2(x):
    if x >= 90:
        print("A")
    if x >= 80:
        print("B")
    if x >= 70:
        print("C")
    if x >= 60:
        print("D")
    else:
        print("F")

Can you spot the error in the code above? Again, for what input scores will this print the right letter?

In [7]:
# Use this box to call the function `printGradeIncorrect2(x)` and see what happens.

Modify the code above (printGradeIncorrect2 function) to make it correct. Make sure it only prints one letter grade for each input and that it prints the correct letter grade.

How can you verify that your function is correct? Write some test cases to verify your solution.

In [9]:
# Write some tests cases here (e.g. `printGradeIncorrect2(55) == 'F'` and more...)

Question 5

Different ages correspond to different school in Ethiopia. This shows these categories:

0 - 5     No School

6 - 13    Elementary School     

14 - 18   High School

19 - 22   University

23 - 100  No School   

5.1

Write a variable for Daniel that stores his age (an integer between 0 and 100).

Now using this variable, how would you write a conditional to check if Daniel is in elementary school? If this is True, print the string "Elementary School".

In [11]:
# Write code here to verify if Daniel is in "Elementary School" using conditionals (`if`, `elif`, `else`)

5.2

Similar to above, how would you write a conditional to check if Daniel is in the "No School" category? Make sure to verify both cases ("Elementary School" and "No School") and if the age is in those ranges, print the string "No School".

In [6]:
# Write code here to verify if Daniel is in "Elementary School" or "No School" using conditionals (`if`, `elif`, `else`)

5.3

Write a function isInSchool(age) where age is an integer between 0 and 100, that either returns "No School" if the person is not in school or "School" if the person is in school.

In [12]:
# Write a function here to verify if someone is in "School" or "No School" using conditional (`if`, `elif`, `else`)

5.4

Now using the code pieces you just wrote and your knowledge of conditionals, write a function scoolCategory(age) that will take in an age integer between 0 - 100 and prints the category of school they are in (string). Try to do this using only one if statement.

In [14]:
def schoolCategory(age):
    # Complete the function here using the code from 5.1 to 5.3
    return

Question 6

6.1

Create a list storing five (5) different integers. Store this in a variable called x.

In [15]:
# Create the list here

6.2

Using list indexing print the first and last values in the list. For the last value, do this two ways:

1) using -1

2) NOT using -1

In [16]:
# Write code to print the first value here

# Write code to print the last value for method 1 here (using -1)

# Write code to print the last value for method 2 here (NOT using -1)

6.3

Using slicing on list x make another list y containing the second to fourth elements inclusive. Print y and verify it is in fact the correct slicing.

In [17]:
# Write code to make another list `y` here 

6.4

Change the first value of y to be "hello", without making a new list.

In [18]:
# Write code to change the first value here

6.5

Using the len() function, print the length of x and the length of the first element of y (which should now be the string "hello").

In [21]:
# Write code here to print the lengths of `x` and the first element of `y`

Using code show that x and the first element of y are the same lengths.

In [22]:
# Write code here to show the lengths of `x` and the first element of `y` are the same

However, also using code and the type function, show they are not the same type.

In [23]:
# Write code here to show the lengths of `x` and the first element of `y` are not the same type

Question 7

Write a function verifyInteger(x) that takes in an integer x and prints if it is "positive", "negative" or "zero".

In [24]:
# Define your function verifyInteger here

Question 8

Write a function listLen(l) that takes in a list l and returns the length of the list if the list is not empty. If the input is the empty list, return "this is empty".

In [25]:
# Define your function listLen(l) here

Question 9

Write a function allEqual(l) that takes in a list l and returns True if all the elements in the list are equal and False otherwise. You do not need for loops for this. Hint: You can multiply lists with integers and you can compare two lists to check if they are equal.

allEqual([1,1,1]) == True
allEqual([]) == True
allEqual([1,2]) == False
allEqual(["salaam", "salaam"]) == True
In [26]:
# Define your function allEqual(l) here

Question 10

You are given two lists of strings called names and cities. The first person in names lives in the last city in cities, the second person lives in the second to last city, the third lives in the third to last, and so on. Write code to create a third list called inOrder such that the even indexes (0, 2, 4, etc.) are the names of the people (in order) and that the odd indexes (1, 3, 5, etc.) are the cities. For a person in index $i$, their corresponding city should be in index $i+1$.

For example:

names = ["Daniel", "Nati", "Jelani"]
cities = ["Cambridge","Addis Ababa", "San Fransisco"]

In this case,

- Daniel lives in San Francisco
- Nati lives in Addis Ababa
- Jelani lives Cambridge


You should create the final list:

inOrder = ["Daniel","San Fransisco", "Nati", "Addis Ababa", "Jelani", "Cambridge"]
In [28]:
names = ["Timnit", "Binam", "Basi"]
cities = ["Harar", "Addis Ababa", "Gondar"]
In [27]:
# Write code to create `inOrder` list from `names` and `cities` lists

Question 11

Write a function round(x) that takes in a number x and returns the rounded version of that number.

For example, round(1.2) = 1

Similarly, round(2.6) = 3

In [29]:
# Write the function `round(x)` here

Question 12

Write a function addFractions(l0, l1) that takes in 2 lists l0 and l1 where each list represents a fractional number where the first number is the numerator and the second is the denominator.

For example, $[2,1] => \frac{2}{1} = 2$, (Numerator is 2, denominator is 1)

For example, $[3,4] => \frac{3}{4} $, (Numerator is 3, denominator is 4)

We want to return the sum of these two fractions.

For example, addFractions([3,4], [2,3]) should return [17, 12] because $\frac{3}{4} + \frac{2}{3} = \frac{17}{12}$

In [30]:
# Write your `addFractions(l0, l1)` function here 

Question 13

Write a function costToM(n, m, upcost, downcost) that takes in four (4) integers, n, m, upcost, downcost. We want to know the cost to make n a multiple of m.It costs amount upcost for every increment ($+$) of 1 and costs amount downcost for every decrement ($-$) of 1.

Return the cheapest cost to get from n to a multiple of m.

For example, costToM(14, 5, 1, 1) should return 1 because you can get to 15 (a multiple of 5) with cost 1 and you can get to 10 (a multiple of 5) with cost 4.

costToM(14, 5, 20, 1) should return 4 because you can get to 15 (a multiple of 5) with cost 20 and you can get to 10 (a multiple of 5) with cost 4.

In [31]:
# Write your function `costToM(n, m, upcost, downcost)` here

Question 14

Write a function calcArea(p0, p1) that takes in 2 points p0, p1 where the first is the bottom left coordinate (x0, y0) and the second is the top right coordinate (x1, y1) of a rectangle. Return the area of the rectangle.

For example, calcArea((1,1), (4,5)) should return $4*3 = 12$.

title

In [32]:
# Write function `calcArea(p0, p1)` here

Question 15

15.1

Write a function overlappingRectangles(l1, r1, l2, r2) that takes in 4 points l1, r1, l2, r2. The first 2 points are the bottom left coordinate and top right coordinates of the first rectangle. The second 2 points are the bottom left and top right coordinates of the second rectangle. Return True if the 2 different rectangles overlap.

For example, with the image below we would call the function with inputs as such: overlappingRectangles((2,2), (7,3), (8,5), (9,7)), and since they do overlap, return True.

title

In [33]:
# Write overlappingRectangles(l1, r1, l2, r2) function here!

15.2

Write a function areaOverlap(l1, r1, l2, r2) to compute the area of the overlapping rectangles. If the rectangles do not overlap, return 0.

In [34]:
# Write areaOverlap(l1, r1, l2, r2) functiono here!