Classes and Databases: Person

Introduction. This homework is intended to review and extend your knowledge of classes in Python and to practice storing a program’s state in a database between runs. You will be writing the first class in a program that encapsulates the concept behind Facebook. You will finish the program in hw4. Because of the I/O in this and the next assignment, incorrect programs have great potential to hang up the test programs. This will result in a 0, so don't turn in modules that crash the tests. Instructions. Create a module named hw3.py. Below is the spec for four methods and eight functions. Implement them and upload your module to the D2L dropbox. Testing. Download hw3_test.py and auxiliary testing files and put them in the same folder as your hw3.py module. Run it from the command line to see your current correctness score. Each of the methods and functions is worth 8.33% of your correctness score. You can examine the test module in a text editor to understand better what your code should do. The test module is part of the spec. The test file we will use to grade your program will be different and may uncover failings in your work not evident upon testing with the provided file. Add any necessary tests to make sure your code works in all cases. Documentation. Your module must contain a header docstring containing your name, your section leader’s name, the date, ISTA 350 Hw3, and a brief summary of the module. Each method/function must contain a docstring. Each docstring should include a description of the function’s purpose, the name, type, and purpose of each parameter, and the type and meaning of the function’s return value. Grading. Your module will be graded on correctness, documentation, and coding style. Code should be clear and concise. You will only lose style points if your code is a real mess. Include inline comments to explain tricky lines and summarize sections of code (not necessary on this assignment). Collaboration. Collaboration is allowed. You are responsible for your learning. Depending too much on others will hurt you on the tests. “Helping” others too much harms them in reality. Cite any sources/collaborators in your header docstring. Leaving this out is dishonest. Resources. https://docs.python.org/3.4/tutorial/index.html https://docs.python.org/release/2.5.2/lib/string-methods.html https://docs.python.org/3.4/tutorial/classes.html https://docs.python.org/3/library/sqlite3.html http://www.sqlite.org/index.html Nice pages on creating decorators (examples are in Python 2). However, you will see the * operator (not multiplication), which we haven't learned. It is variously called star-args, the splat operator, and the unpack operator. It packs/unpacks sequence objects. Warning: these pages are likely to look like mumbo-jumbo at this point. http://www.artima.com/weblogs/viewpost.jsp?thread=240808 http://www.artima.com/weblogs/viewpost.jsp?thread=240845 class Person: init: Each Person object has four instance variables, called first, last, bday, and email, and init has four corresponding string parameters, each of which has the empty string as a default argument. The first parameter is the Person’s first name, the second the last name, the third his/her birthday, and the last the Person’s e-mail. If any of the parameters are the empty string, get a value from the user using one of the following prompts: Enter person's first name: Enter person's last name: Enter person's birthday: Enter person's e-mail: Each colon is followed by a space. repr: This method returns a string in the following format: 'Rich Thompson: 5/21, rm@g'. read_person: This is a class method that reads the data necessary from a text file to create and return a Person instance. It takes one argument, a file object (not a filename). It reads a line from the file. If the line is empty, return False. Otherwise, use the contents of this and the next three lines as the first name, last name, birthday, and e-mail of a new Person. Remember to use the classmethod decorator. This method allows one to traverse a file of Person objects, or perhaps Person objects with some other data interspersed, and read and create one Person object from it at a time. write_person: This instance method takes one argument, a file object. It writes the instance variables, one per line, to the file in this order: first, last, birthday, email. -------------------------------------------------------------------------------------------------------------------------------------- open_persons_db: Read the os.path documentation to learn how to determine if a file exists. Determine whether or not persons.db exists and store this information in a variable. Connect to persons.db. Set its row_factory to sqlite3.Row. If it's a new database, create friends and colleagues tables with column names first, last, bday, and email. These are all TEXT fields. email is the primary key. Return the database. add_person: This function has four parameters. The first is a Person database as described above. The second is a Person object. The third is a Boolean with a default argument of True that tells the function if the Person is a friend. The last is a Boolean with a default argument of False that tells the function if the Person is a colleague. If both Booleans are False, print the following message and return False: 'Warning: <email address not added – must be friend or colleague'. By default, the print function prints to stdout. Print your warning to stderr. To do this, import sys, then pass sys.stderr to the print function using the keyword file. (In Powershell, there is no visible difference between printing to stdout and stderr. In many other programs, text printed to stderr will print to the console in red.) Otherwise, insert the Person into the appropriate tables and return True. Don't forget to commit your changes to the database. delete_person: This function takes a Person database and a Person. Delete the Person from all tables. to_Person_list: This function takes a cursor object as its sole argument and returns a list of Person objects constructed from the data in the rows iterated over by the cursor. The following functions should use to_Person_list: get_friends: This function takes a Person database as its sole argument and returns a list of Person objects representing all of the friends in the database. get_colleagues: This function takes a Person database as its sole argument and returns a list of Person objects representing all of the colleagues in the database. get_all: This function takes a Person database as its sole argument and returns a list of Person objects representing all of the friends and colleagues in the database without duplicates. get_and: This function takes a Person database as its sole argument and returns a list of Person objects representing all of the people who are both friends and colleagues in the database.