To Lecture Notes

IT 211 -- Feb 20, 2019

Review Exercises

  1. What does this PPM image display?
    P3 3 3 255
192 192 192  0 0 255  192 192 192
  0   0 255  0 0 255    0   0 255
192 192 192  0 0 255  192 192 192
    a. A black X            b. A blue cross
    c. A yellow box       d. A teal L
    Ans: b, a blue cross. 0 0 255 are the color components for blue.
  2. What is a list? We already know about lists from this statement:
    fields = line.split(",")
    Ans: A list is a sequence of items like a = [3, 2, 5, 4] or b = ["dog", "cat", "mouse"]. The items are accessed by zero-basec index: a[0] is 3; b[1] is "cat".
  3. What is the output?
    1. a = [4, 1, 7, 5, 8]
print(a[3])
# Output: 5

    2. a = [4, 1, 7, 5, 8]
print(a[4] - a[1], a[4 - 1], a[-2])
      a[-2] is the second item from the end of the list.
    3. a = [4, 1, 7, 5, 8]
total = 0
for n in a:
    total += n
print(total)

# Output: 25

    4. t = 1
s = "2 1 4 6"
a = s.split(" ")
for val in a:
    t *= int(val)
print(t)

# Output: 48
  4. Write a script that inputs a string, converts it to a list, and prints the list. Ans:
    s = input("Input a string: ")
lst = list(s)
print(s)
    We can combine these three lines into one like this:
    print(list(input("Input a string: ")))
  5. Select four list methods from the Builtin Methods Document and test them.
  6. Test the str method join. Ans:
    s = ["d", "o", "g"]
t = ":".join(s)
u = "".join(s)
print(t)
# Output:
d:o:g
dog

Practice Problems

  1. Write and test user defined standalone methods using the following specs:

    Method Name Input Parameter(s) Return Value Side Effects*
    rm_vowels input_string Input string with vowels removed None
    factors number List of factors None

    *Because neither method has any side effects, this means that each of these methods can only return a value, it can't do anything else like print to the screen or write to a file.

    Here are two scripts that you can convert into the methods specified in the preceding table.
    1. # Remove vowels
input_str = print("Enter input string: ")
input_str = gets.chomp
output_str = ""
for letter in input_str:
    letter = letter.upper( )
    if letter != 'A' and letter != 'E' and letter != 'I' \ 
       letter != 'O' and letter != 'U':

        output_str += letter

print("String without vowels", output_str)

# Ans:
def rm_vowels(input_string):
    output_str = ""
    for letter in input_str:
        letter = letter.upper( )
        if letter != 'A' and letter != 'E' and letter != 'I' \ 
           letter != 'O' and letter != 'U':

            output_str += letter

    return output_str
    
string = print("Enter input string: ")
processed_string = rm_vowels(string)
print("String without vowels", processed_string)

    2. # Obtain list all factors of input integer.
n = int(input("Enter a positive integer: "))
factors = [ ]
for f in range(2, n):
    if n % f == 0
        factors.append(f)
        
print(factors)

# Ans:
def factors(number):
    # 1 and number are always factors so we can
    # add them to the list without checking.
    factors = [1]
    for f in range(2, number):
    if number % f == 0
        factors.append(f)
    factors.append(number)
    return factors
    
n = int(input("Enter a positive integer: "))
print(factors(n))

Project 5