1. Your Django application is built for paranoids who want a complete audit trail of any changes made to the data. The audit should contain any modification made to any attribute of the model and include the time of change and by which user. How would you approach this?

2. Create a function that receives one argument of any type and always returns a list of strings. If the argument is a dict, return a list of the keys. If it's a number, return a string representation of it as a list, etc. Bonus points if it can be done without explicitly checking the argument type inside the function body.

   Sample output:

   >>> to_list([1, 2, 3])
   ['1', '2', '3']
   
   >>> to_list({'one': 1, 'two': 2})
   ['one', 'two']
   
   >>> to_list('value')
   ['value']
   

3. Given two lists (of same length): l1 = ['a', 'b', 'c', 'd'] and l2 = [1, 2, 3, 4]

   Create a function that returns a dict where each element of l1 is the key and its value is the corresponding element from l2. Bonus points if you can explain how you'd deal with lists of different lengths.

4. Write a small self-contained python command line tool that receives a list of URLs as command line arguments and returns a structured JSON data containing all the links and image urls within the document. The tool should be generic enough to work with any URL. Don't spend more than an hour or two on this. The result should include everything to make it usable (requirements file, etc.), and tests to ensure it works as expected.

   It should be executed as:

   ./mytool http://example.com http://bbc.co.uk
   

   And return:

   {
   		"http://example.com": {
   				"links": [
   						"https://example.link1.com",
   						"https://example.link2.com"
   				],
   				"images": [
   						"https://example.link.com/image/one.jpg",
   						"https://example.link.com/images/two.png"
   				]
   		},
   		"http://bbc.co.uk": {
   				.....
   		}
   }
   

Solutions were tested with Python 2.7+

1. You can use the django-simple-history and django-audit-log libraries to achieve this quickly and cleanly:

   # Assumes libs are correctly set up
   from audit_log.models import AuthStampedModel
   from simple_history.models import HistoricalRecords
   
   
   # Base for each of our models to inherit from.
   # django_extentions' TimeStampedModel should not be necessary as it looks 
   # like created and modified times are already tracked by simple_history. 
   class TrackedModel(AuthStampedModel):
       history = HistoricalRecords()
   
   # Example model to track
   class Poll(TrackedModel):
       question = models.CharField(max_length=200)
       pub_date = models.DateTimeField('date published')
   
   
   # After having created and modified poll instances:
   # Grab the second last saved poll state
   >>> poll_state = Poll.history.all()[1]
   

   Now poll_state has created_by, modified_by and history_date attributes.

2. See 2.py

3. See 3.py

4. See 4:

   Setup

    cd 4
    pip install -r requirements.txt
   

   Running program

   To run as an executable run chmod +x mytool.py; other wise run as python mytool.py ....

   Changed mytool to mytool.py so we can import functionalites in our test file.

    ./mytool.py http://example.com http://bbc.co.uk
   

   Running tests

    pytest -v