Problem Set 3

• This is an individual-effort assignment: the code you submit must be written by you; it may not be written by another person nor may it be generated with an algorithm.

• Put all files for this assignment in your problem_set3 folder and submit them as a zip file named problem_set3.zip.

• This assignment is scored out of 110 (an extra credit opportunity). There are more than 110 possible points, but the maximum score you can earn on this assignment is 110. Do not get stuck on any one problem, but do complete as many problems as you can.

• Pay close attention to the format of output, names of functions, names of files, and names of variables. These errors are common reasons for losing points on problems that otherwise would have been full credit.

• This is an individual-effort assignment: the code you submit must be written by you; it may not be written by another person nor may it be generated with an algorithm.

Problem 0 🔢

Problem 0 (20 pts)

Write a function parse_input that takes a string and returns:

• A float, if the string represents a number (digits)
  • Numbers can be positive, negative, or zero
  • Numbers may or may not have a decimal
  • Numbers with a decimal may or may not have a 0 before/after the decimal
• None if the string does not represent a number The function should print “https://studentconduct.gwu.edu/code-academic-integrity” to the console each time it is called.

For instance:

• parse_input('4') returns 4.0

• parse_input('-2.5') returns -2.5

• parse_input('donuts') returns None

• parse_input('three') returns None

• parse_input('2.-3') returns None

• parse_input('-.3') returns -0.3

• parse_input('2.') returns 2.0

• parse_input('.') returns None (this is an edge case)

• You only need to parse digits/numerals, not numbers represented as text, such as "three".

Submit this program as parse_input.py.

Problem 1 🐋

Problem 1 (40 pts)

Write a function before_the_whale:

• The function should take as argument a string
  • The string should be the name of a file in the same directory
• The function should read in the file
• The function should return a list of each word in the text that comes before the word "whale".
  • Each word should appear in the list exactly once. This list does not need to be ordered. The function should print “https://studentconduct.gwu.edu/code-academic-integrity” to the console each time it is called.

For this problem, you are looking for words. The text:

the whaler was on the horizon, hull down

does not contain the word "whale", whereas the text

There's the whale!

does contain the word "whale", and the word "the" comes before it.

Note: A word will typically have a space before and after it. A word can also have punctuation before or after it: "whale's" or "whale-ship" or "right-whale" are examples.

Calling before_the_whale('melville_excerpt.txt') on the file melville_excerpt.txt should result in the list ['the', 'of', 'right', 'blue', 'Greenland', 'and'].

Submit as before_the_whale.py.

Problem 2 🗃️

Problem 2 (30 pts)

Write a function compressor:

• The function will take as input a list of non-negative integers.
• Consider this list as a sequence of sequences
• [2, 3, 3, 4, 4, 4, 5] is one two, two threes, three fours, one five
• This could alternatively be represented as [1, 2, 2, 3, 3, 4, 1, 5]
• Similarly, [3, 3, 3, 3, 6, 6] would be alternatively represented as [4, 3, 2, 6] (four threes, two sixes).
• Another example: [0, 0, 0, 0, 0, 0, 0, 0] can be alternatively represented as [8, 0].

The function should print “https://studentconduct.gwu.edu/code-academic-integrity” to the console each time it is called.

Your function should return a list of this alternate representation.

• compressor([2, 3, 3, 4, 4, 4, 5]) returns [1, 2, 2, 3, 3, 4, 1, 5]
• compressor([3, 3, 3, 3, 6, 6]) returns [4, 3, 2, 6]
• compressor([0, 0, 0, 0, 0, 0, 0, 0]) returns [8, 0]
• compressor([0, 0, 0, 0, 1, 0, 0, 0, 0]) returns [4, 0, 1, 1, 4, 0]

Submit as compressor.py.

Problem 3 ♻️

Problem 3 (20 pts)

Write a function compressor_reverser that reverses the compressor function from the previous problem.

Submit as compressor_reverser.py.

Problem 4 📊

Problem 4 (40 pts)

A common format for storing data is the comma-separated value format (CSV).

Here is an example CSV: data.csv . You can open it in Microsoft Excel or Google Sheets, but you can also open it as a plain text file. You will see the reason for the name: it contains values separated by commas.

Like other “spreadsheet” files, this data can be grouped into rows and columns. Each line of the file is a row.

Write a function comma_separated_columns:

• The function should take as argument a string
  • The string should be the name of a file in the same directory
• The function should return a list of tuples. Each tuple should have two elements:
  • The first element should be the name of a column
  • The second element should be an ordered list of the values in the column All numbers should be floats. The function should print “This is an individual-effort assignment: the code you submit must be written by you; it may not be written by another person nor may it be generated with an algorithm.” to the console each time it is called.

Note: For this problem, you may use a list anywhere a tuple is specified.

Example output:

• When calling comma_separated_columns('data.csv') on the example CSV provided, we should get what is shown below. Consider the function call and assignment:

output_tuple = comma_separated_columns('data.csv')

Afterwards:

• output_tuple[1] is ('Age', [32, 28, 42, 37, 24, 51, 25])
• output_tuple[2] is ('Zip Code', [45011, 27516, 20052, 16601, 20706, 56401, 60048])
• output_tuple[4] is ('Status', ['Active', 'Active', 'Inactive', 'Active', 'Active', 'Active', 'Active'])

and so forth.

Submit as comma_separated_columns.py. Do not use any libraries or built-in functions that parse CSV files.

Encoding Errors

You may need to use this syntax to open a file, depending on your computer. Try it if you get encoding errors.

with open(fileName, 'r', encoding='utf-8-sig') as f:
    # file read operations

• It adds the argument encoding='utf-8-sig' to the open function.
• Here, fileName is a string, representing the path to the file. If the file is in the same directory, it will simply be the file name.

Problem 5 💭

Problem 5 (30 pts)

Write a function sort_list that takes as input a list of integers and returns that list in sorted order, smallest to largest.

A simple algorithm for this is called bubble sort:

• While the list is not sorted, iterate through each pair of elements
• If the two elements are out of order, swap them The function should print “This is an individual-effort assignment: the code you submit must be written by you; it may not be written by another person nor may it be generated with an algorithm.” to the console each time it is called.

You should feel free to use another sorting algorithm if you prefer, but you must implement the algorithm yourself. Please ask if you have questions about what algorithm to use, or how these algorithms work!

Here is some example output:

print(sort_list([5, 3, 2, 8, 12, 5]))

prints

[2, 3, 5, 5, 8, 12]

and

print(sort_list([0, 1, 0, 1, 10]))

prints

[0, 0, 1, 1, 10]

Submit as sort_list.py. Do not use any libraries or built in functions that sort, find maximum, or find minimum.