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Study Guide

##Q:

Color Class

  • Create a class called "Color" that will store a tuple of (r,g,b).
  • The tuple should be stored in a data member called color.
  • The components of the color tuple should be stored in data members: red, green, blue as well
  • Add a str method to print out the color class so it looks like: "(red: redVal, green: greenVal, blue: blueVal)"
  • Here is some usage:
c1 = Color((255,0,0))
print(c1.red)
#prints: 255

c1.blue = 255
print(c1)
#prints: (red: 255, green: 0, blue: 255)

c1.setColor((0,0,0))
print(c1)
#prints: (red: 0, green: 0, blue: 0)

##Q:

Overload the addition operator so that we can add two colors. Adding colors is a pretty wierd experience, so we will create our own addition method. Basically we will average each color.

For example:

c1 = Color(255,255,255)
c2 = Color(0,0,0)
c3 = c1 + c2

print(c3)
#prints: (red: 128,green: 128,blue: 128)

##Q:

Grayscale Class

This class will extend the color class.

So what is gray scale? Its where you take the 3 individual parts of a color and using those values you calculate a single value that will be assigned to each of the 3 components, making it some shade of gray.

For example here is red: (0,255,0) and here is the gray scale equivalent: (85,85,85) (using the average method from below).

Your GrayScaler class is serious about its grayscalin` powers and has three methods to turn a color into its monochromatic equivalent:

  • lightness
  • average
  • luminosity
  • custom

Lightness

The lightness method averages the most prominent and least prominent colors: (max(R, G, B) + min(R, G, B)) / 2.

Average

The average method simply averages the values: (R + G + B) / 3.

Luminosity

This method also averages the values, but it forms a weighted average to account for human perception. We’re more sensitive to green than other colors, so green is weighted most heavily. The formula for luminosity is 0.21 * R + 0.72 * G + 0.07 * B

Custom

This method allows the user to pass in three floats to act as the weights in your formula: w1 * R + w2 * G + w3 * B

Here is some example usage to help you determine how to design your class:

myColor = (255,0,0)
grayish = GrayScaler(myColor)
gray1 = grayish.Average()
gray2 = grayish.Custom(.33,.44,.23)


grayish2 = GrayScaler() # defaults to black in the class if no color provided
grayish2.SetColor(255,192,203)
gray3 = grayish2.Luminosity()
"""
@Description: Gets an RGB color represented as a tuple, and converts it to a 
				gray scale equivalent based on chosen method.
@Methods:
    Lightness - as described above
    Average - as described above
    Luminosity - as described above
    Custom - as described above
    SetColor - Lets user change the color originally passed in.
"""
class GrayScaler(Color):

Q:

Create a point class, line class, and a rectangle class.

  • A point is a tuple of two integers: (3,6)
  • A line consists of two points: (3,6),(7,8)
    • Add a length method
  • A rectangle consists of two points as well, the upper right, and the lower left.
    • Add an area and perimeter method

Q:

class Person(object):

    def __init__(self, name, age):
        self.name = name
        self.age = age

    def is_old(self):
        return self.age > 40

        
person = Person('G. H. Hardy', 70)  
print person.is_old() # Prints True

Write a Student class that extends the Person class and add a method: is_honor_student that would print True if the students gpa is greater than 3.0

student = Student('G. H. Hardy', 70, 4.0)
print student.is_old()	# prints True
print student.is_honor_student()	# prints True

Q:

Run a binary search on the following values looking for key=55. Show the index values for first mid and last at each iteration.

0 1 2 3 4 5 6 7 8 9 10
0 5 13 19 22 41 55 68 72 81 98

Q:

Write a function that removes all instances of an element from a list.

def remove_all(el, lst):
"""Removes all instances of el from lst.
>>> x = [3, 1, 2, 1, 5, 1, 1, 7]
>>> remove_all(1, x)
>>> x
[3, 2, 5, 7]
"""

Q:

Given a list of words like so:

words = [
   'look', 'into', 'my', 'eyes', 'look', 'into', 'my', 'eyes',
   'the', 'eyes', 'the', 'eyes', 'the', 'eyes', 'not', 'around', 'the',
   'eyes', "don't", 'look', 'around', 'the', 'eyes', 'look', 'into',
   'my', 'eyes', "you're", 'under'
]

Write a python snippet to find the words that occur most often. You output should look something like the following:

[('eyes', 8), ('the', 5), ('look', 4)]

Q:

Write a class called book_analysis that will do a word frequency analysis on a book. You can assume that the book has had all punctuation removed. Your class should count the number of unique words and be able to return the nth most frequent word. Below is some code that WILL actually do what I'm asking you to do (but not in a class).

import string
import operator

#url for book = http://www.gutenberg.org/files/2701/2701.txt
#go to url and save book as moby_dick.txt on your computer
f = open('moby_dick.txt')


dict = {}

for line in f:
    exclude = set(string.punctuation)
    words = ''.join(ch for ch in line.strip() if ch not in exclude).lower()
    for word in words.split(' '):
        if not word in dict:
            dict[word] = 0
        dict[word] += 1

sorted_dict = sorted(dict.items(), key=operator.itemgetter(1), reverse=True)

print(sorted_dict)

The sorted_dict looks like:


[('the', 14508), ('of', 6701), ('and', 6434), ('a', 4690), ('to', 4658), ('in', 4202), ('', 3491), ('that', 2955), ('his', 2520), ('it',2382), ('i', 1943), ('but', 1781), ('with', 1768), ('he', 1749), ('is', 1731), ('as', 1730), ('was', 1637), ('for', 1627), ('all', 1493),('this', 1411), ('at', 1326), ('by', 1219), .... ('repute', 1), ('aftman', 1), ('incredibly', 1), ('flexion', 1), ('shakespeares', 1), ('coursefor', 1), ('scabbards', 1), ('causesuch', 1), ('filial', 1), ('barwait', 1), ('hornsofplenty', 1), ('sash', 1), ('races', 1), ('linenow', 1), ('andromedaindeed', 1)]

where the word and occurence are in a tuple.

Your job is to organize into class form. Lets assume the constructor will load the book. Here is some usage:

anlyz = BookAnalysis('moby_dick.txt')
most = anlyz.getnth(3)
print(most)
# ('and', 6434)
x = anlyz.occurs('barwait')
print(x)
# barwait occurs 1 times
print(anlyz.totalWords())
# total words: 20211

Some of the methods return a printed message (e.g. "barwait occurs 1 times"), this is ok for this test problem, but normally methods do not print messages and return values!

Q:

import random

nums = []

for i in range(100):
	nums.append(random.randint(0,500))

searchKey = random.randint(1,100)
print(searchKey)

nums.append(searchKey)

nums = sorted(nums)

print(nums)

f = 0 
l = len(nums)
m = (f + l) // 2



Found = False

while not Found:
	if nums[m] == searchKey:
		Found = True
		print(m)
	if searchKey > nums[m]:
		f = m 
	else:
		l = m 
		
	m = (f + l) // 2