Overview

When making back up of data files or log files, it is a very common practice to name the backup directories and/or files based on the date the backup was done. In order to restore or locate the directory/file, we often need to find out the backup date from today's date.

The computational task for this assignment is to design an algorithm and write a python script according to your algorithm with appropriate functions. The script should take a date in the "YYYY/MM/DD" format and the number of days before or after the given date as the command line arguments, calculate and output to the standard output data channel the targeted date which is the number of day before or after the given date in the same format.

Coding Standard

Your python script must follow the following coding guide:

PEP-8 -- Style Guide for writing Python Code

Command Line Argument to be supported

Name your python script as a1_[student_id].py, where [student_id] is your Seneca email user name.
Your python script must support two mandatory command line arguments : (1) any valid date in YYYY/MM/DD format, (2) number of days before or after the given date, and one option flag: "--step"
If there are less or more than two data items provided at the command line, your script should display the correct usage message and exit.

Class Requirements

Programmer-defined object type: Date

Data Attributes: year, month, and day as integer
Method attributes: tomorrow(), yesterday(), day_of_week()
Operator Overloading:
- '+': perform addition for two Date() object, and one date object and an integer.
- '-': perfome substraction for two Date() object, and one date object and an integer
Special methods:
- __init__(self): Date object constructor
- __repr__(self): return date object as a string in "yyyy-mm-dd" format
- __str__(self): return date object as a string in "yyyy:mm:dd" format
Supporting function:
- days_to_time(): convert an integer which is n days from epoch (Jan 1, 1970) to a corresponding date object.

Required Modules and Functions

Your python script is allowed to import only the os and sys modules from the standard library and all the built-in functions.

Based on the algorithm you have designed for this assignment, you should at least have the following three methods defined in your class file for Date (see later section on the purpose of each function) in order to get a passing grade for this assignment:

tomorrow()
yesterday()
sum_date()
diff_date()

You can also create additional functions to improved the re-usability of your python code by adding the following functions to earn the maximum possible mark for this assignment:

days_in_mon()
leap_year()
valid_date()
usage()

Documentation

Please use python's docstring to document your python script (script level documentation) and each of the functions (function level documentation) you created for this assignment. The docstring should describe 'what' the function does, not 'how' it does.
The following shows the docstring that was added to the after() function which provides the following information when called with help(after) in the python interactive shell:

Authorship Declaration

All your Python code for this assignment must be placed in a single source python file. Please include the following declaration as part of the docstring in your Python source code file (replace "Student Name" with your own name):

OPS435 Assignment 2P - Fall 2019
Program: a1_[student_id].py (replace student_id with your Seneca User name)
Author: "Student Name"
The python code in this file (a1_[Student_id].py) is original work written by
"Student Name". No code in this file is copied from any other source 
except those provided by the course instructor, including any person, 
textbook, or on-line resource. I have not shared this python script 
with anyone or anything except for submission for grading.  
I understand that the Academic Honesty Policy will be enforced and 
violators will be reported and appropriate action will be taken.

Tests and Test results

You must name your class definition python script for Date as a2_class.py. The following test scripts are for testing your class definition. The test scripts can be used to test the date objects created by using your Date class.

Please review those tests that failed and try to fix it in your class definition to address any bugs you may have.

Test for tomorrow and yesterday methods

Start up an interactive Python session and issue the following python statments:

[raymond.chan@mtrx-node04pd a2p]$ python3
Python 3.6.8 (default, May  2 2019, 20:40:44) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from a2_class import *
>>> dir()
['Date', '__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'daysb4month', 'int_to_date']
>>> d1 = Date(2019,11,6)
>>> d1.tomorrow()
2019-11-07
>>> d1.yesterday()
2019-11-05
>>> print(d1.tomorrow())
2019/11/07
>>> print(d1.yesterday())
2019/11/05
>>> d2 = Date(2019,2,28)
>>> d2.tomorrow()
2019-03-01
>>> d2.yesterday()
2019-02-27
>>> d3 = Date(2016,2,28)
>>> d3.tomorrow()
2016-02-29
>>> d3.yesterday()
2016-02-27
>>> d4 = Date(2018,12,31)
>>> d4.tomorrow()
2019-01-01

Test for operator overloading '+' and '-'

>>> d2
2019-02-28

>>> d2 + 1
2019-03-01

>>> d2 + 2
2019-03-02

>>> d3
2016-02-28

>>> d3 + 1
2016-02-29

>>> (d3 + 1) - 1
2016-02-28

>>> d3 - 1
2016-02-27

>>> d4
2018-12-31

>>> d4 + 365
2019-12-31

>>> d4 - 365
2017-12-31

Test for day of the week method

Script structure and sample template

Your code should all be in a single python file with at least the functions mentioned above: dbda(), after(), and before(). To earn the maximum mark, you should also create additional functions into your algorithm, e.g.: leap_year(), days_in_mon, valid_date(), usage(), etc

The following is a brief description of each function:

The dbda() function should be the main function of your script. The dbda() function will take a date in "YYYY/MM/DD" format, a positive or negative integer, and return a date either before or after the given date according to the value of the given integer in the same format. Your dbda() function should delegate the actual calculation of the target date to either the after() function or the before() function.
The before() function will take a date in "YYYY/MM/DD" format and return the date of the previous day in the same format.
The after() function will take a date in "YYYY/MM/DD" format and return the date of the next day in the same format. Next paragraph is a sample python code for the after() function. To earn the maximum possible mark for the assignment, you should modify the sample after() function to make use of the days_in_mon() function.
The leap_year() function will take a year in "YYYY" format, and return True if the given year is a leap year, otherwise return False.
The valid_date() function will take a date in "YYYY/MM/DD" format, and return True if the given date is a valid date, otherwise return False plus an appropriate status message. The valid_date() function should make use of the days_in_mon() function.
The days_in_mon() function will take a year in "YYYY" format, and return a dictionary object which contains the total number of days in each month for the given year. The days_in_mon() function should make use of the leap_year() function.
The usage() function will take no argument and return a string describing the usage of the script.

     #!/usr/sbin/env python3
     ''' docstring 
     '''
     import ...

     def after(today):
        ....
        return next_day

     def before(today):
        ....
        return previous_day

     ....

     def dbda(date,days):
        ...
        setup loop:
           call after() or before() as appropriate
        return target_day

     if __name__ == "__main__":

     .. processing command line arguments ..
     .. call dbda() 
     ...
     .. output the result

Sample code for the after() function

# Return the date in YYYY/MM/DD after the given day
# 
def after(today):
    if len(today) != 10:
       return '0000/00/00'
    else:
       str_year, str_month, str_day = today.split('/')
       year = int(str_year)
       month = int(str_month)
       day = int(str_day)

       lyear = year % 4
       if lyear == 0:
          feb_max = 29 # this is a leap year
       else:
          feb_max = 28 # this is not a leap year

       lyear = year % 100
       if lyear == 0:
          feb_max = 28 # this is not a leap year

       lyear = year % 400
       if lyear == 0:
          feb_max = 29 # this is a leap year

       tmp_day = day + 1 # next day

       mon_max = { 1:31, 2:feb_max, 3:31, 4:30, 5:31, 6:30, 7:31, 8:31, 9:30, 10:31, 11:30, 12:31}
       if tmp_day > mon_max[month]:
          to_day = tmp_day % mon_max[month] # if tmp_day > this month's max, reset to 1
          tmp_month = month + 1
       else:
          to_day = tmp_day
          tmp_month = month + 0

       if tmp_month > 12:
           to_month = 1
           year = year + 1
       else:
           to_month = tmp_month + 0

       next_date = str(year)+"/"+str(to_month).zfill(2)+"/"+str(to_day).zfill(2)
     
       return next_date

Normal task

Your script must be able to take two dates both in "YYYY/MM/DD" format and output the number of days between the given two dates. e.g.

Calculate the number of days between "2018/03/01" and "2019/03/01"

 python3 a1_rchan.py 2018/03/01 2019/03/01
 365

Calculate the number of days between "2019/03/01" and "2018/03/01"

 python3 a1_rchan.py 2019/03/01 2018/03/01
 365

Deliverable

Create a private repository on github.com under your account

name the repository as 'ops435-a1'
invite 'rayfreeping' as one of the collaborator to your 'ops435-a1' repository
use this repository for developing the and keeping track of the following text/source code files:
- the algorithm for assignment 1 named "a1_algorithm.txt"
- the python script for assignment 1 named "a1_[seneca-id].py"
- the test results produce by the assignment checking script "checkA1.py". Name it as a1_results.txt

Rubric

Task	Maximum mark	Actual mark
Program Authorship Declaration	5
Program usage	5
Program Options --step	5
after() function	5
before() function	15
dbda() function	10
script level docstring	5
leap_year() function	5
valid_date() function	5
days_in_mon() function	5
usage() function	5
Algorithm	15
github.com repository	15
Total	100

Due Date and Final Submission requirement

Check with your professor for the due date for your section.

Please submit the following files to blackboard by the due date:

your algorithm (step-by-step instruction for solving the computation problem for this assignment in the English language), name the file as 'a1_algorithm.txt'
your python script, name the file as 'a1_[seneca-id].py'
the output of the checking script checkA1.py, name the file as 'a1_results.txt'
the 'git log' output for your own repository 'ops435-a1' on github.com, name the file as 'a1_gitlog.txt'

CDOT Wiki ^β

OPS435 Python3 Assignment 2P

Overview

Coding Standard

Command Line Argument to be supported

Class Requirements

Programmer-defined object type: Date

Required Modules and Functions

Documentation

Authorship Declaration

Tests and Test results

Test for tomorrow and yesterday methods

Test for operator overloading '+' and '-'

Test for day of the week method

Script structure and sample template

Sample code for the after() function

Normal task

Deliverable

Create a private repository on github.com under your account

Rubric

Due Date and Final Submission requirement

CDOT Wiki β

OPS435 Python3 Assignment 2P

Overview

Coding Standard

Command Line Argument to be supported

Class Requirements

Programmer-defined object type: Date

Required Modules and Functions

Documentation

Authorship Declaration

Tests and Test results

Test for tomorrow and yesterday methods

Test for operator overloading '+' and '-'

Test for day of the week method

Script structure and sample template

Sample code for the after() function

Normal task

Deliverable

Create a private repository on github.com under your account

Rubric

Due Date and Final Submission requirement

CDOT Wiki ^β