Naming Convention in Python

About naming convention in Python, including topics discussed in “A Python Æsthetic” by Brandon Rhodes, and some personal note.

NOTICE: Credits for example code snippets and various contents in this presentation (exclude the last part, starting from slide 27) fully go to Brandon Rhodes.

Transcript

1. A Python Æsthetic
   

   View Slide

2. Video: http://pyvideo.org/video/1599/
   
   
   Slides: http://rhodesmill.org/brandon/slides/2012-11-pyconca/
   

   View Slide

3. Video: http://pyvideo.org/video/1676/
   
   
   Slides: http://rhodesmill.org/brandon/slides/2013-03-pycon/
   

   View Slide

4. Name the Ducks
   • Well-factored Nouns
   
   • Relentless Verbs
   
   • Sin of Synecdoche
   
   • Problem of Pluralization
   

   View Slide

5. Well-Factored Nouns
   def main():!
   page = 'http://twitter.com/uranusjr/'!
   download_page(page)
   

   View Slide

6. Well-Factored Nouns
   def main():!
   page = 'http://twitter.com/uranusjr/'!
   download_page(page)!
   !
   def download_page(page)!
   ... = client.get(page)
   

   View Slide

7. Well-Factored Nouns
   def main():!
   page = 'http://twitter.com/uranusjr/'!
   download_page(page)!
   !
   def download_page(url)!
   page = client.get(url)
   

   View Slide

8. Well-Factored Nouns
   def main():!
   page = 'http://twitter.com/uranusjr/'!
   download_page(page)!
   !
   def download_page(url):!
   page = client.get(url)!
   process_page(page)!
   !
   def process_page(page):!
   ... = page.content
   

   View Slide

9. Well-Factored Nouns
   def main():!
   page = 'http://twitter.com/uranusjr/'!
   download_page(page)!
   !
   def download_page(url):!
   page = client.get(url)!
   process_page(page)!
   !
   def process_page(response):!
   page = response.content
   

   View Slide

10. Well-Factored Nouns
    def main():!
    page = 'http://twitter.com/uranusjr/'!
    download_page(page)!
    !
    def download_page(url):!
    page = requests.get(url)!
    process_page(page)!
    !
    def process_page(response):!
    page = response.content
    

    View Slide

11. Well-Factored Nouns
    def main():!
    url = 'http://twitter.com/uranusjr/'!
    download_page(url)!
    !
    def download_page(url):!
    response = requests.get(url)!
    process_page(response)!
    !
    def process_page(response):!
    page = response.content
    

    View Slide

12. Well-Factored Nouns
    • Plan ahead (when you can)
    
    • Refactor often
    
    • Challenge yourself
    

    View Slide

13. Relentless Verbs
    def database():!
    # What does this even do?!
    !
    def get_database():!
    # Gets an instance for me!!
    !
    def create_database():!
    # Creates a database and returns!
    # it for me!
    

    View Slide

14. Relentless Verbs
    def database():!
    # What does this even do?!
    !
    def get_database():!
    # Gets an instance for me!!
    !
    def create_database():!
    # Creates a database and returns!
    # it for me!
    

    View Slide

15. Relentless Verbs
    document.md5()! ! ! # Probably okay!
    !
    document.get_md5()!
    !
    document.calculate_md5()
    

    View Slide

16. [P]racticality beats purity.
    

    View Slide

17. [P]racticality beats purity.
    reversed(iterable)!
    !
    'a'.upper()!
    !
    len(iterable)!
    !
    min(iterable)!
    

    View Slide

18. Relentless Verbs
    • Functions act
    
    • Verbose verbs can be dropped
    
    • Practicality beats purity
    

    View Slide

19. Sin of Synecdoche
    # In medialib.py:!
    def fetch_songs(urls):!
    ...!
    !
    # In songlib.py:!
    def fetch(urls):!
    ...
    

    View Slide

20. Sin of Synecdoche
    # The caller has their choice:!
    !
    from songlib import fetch!
    fetch(...)!
    !
    # or:!
    !
    import songlib!
    songlib.fetch(...)
    

    View Slide

21. Sin of Synecdoche
    • Be obvious
    
    • Don’t repeat yourself
    
    • Let users choose
    

    View Slide

22. Problem of Pluralization
    >>> connections!
    [,!
    ,!
    ]!
    !
    >>> connections!
    {'master': ,!
    'backup': }
    

    View Slide

23. datum
    data
    datum
    datum
    datum
    dataset
    data
    datum
    datum
    datum
    data
    datum
    datum
    datum
    data
    datum
    datasets
    data
    datu
    datu
    datu
    data
    datu
    datu
    datu
    data
    data
    datu
    datu
    datu
    data
    datu
    datu
    datu
    data
    dataset
    data
    datu
    datu
    datu
    data
    datu
    datu
    datu
    data
    

    View Slide

24. Anti-Plural
    connection_set!
    connection_list!
    connection_dict!
    !
    def close_all(connection_seq):!
    ...!
    !
    def reset_all(connection_map):!
    ...
    

    View Slide

25. I still favor plurals
    And documentation is always necessary.
    

    View Slide

26. Problem of Pluralization
    • Plurals can be ambiguous
    
    • There are only so many expressions
    
    • Total anti-plural may be too much
    

    View Slide

27. My Problem
    

    View Slide

28. My Problem
    def user_profile(request, username):!
    user = request.user!
    if user.is_authenticated:!
    if user.username == username:!
    # Show personal page!
    else:!
    # Show public page!
    else:!
    # Show page for anonymous user
    

    View Slide

29. My Problem
    def user_profile(request, username):!
    user = request.user!
    if user.is_authenticated:!
    if user.username == username:!
    # Show personal page!
    else:!
    # Show public page!
    else:!
    # Show page for anonymous user
    

    View Slide

30. My Problem
    >>> user.is_authenticated!
    >
    

    View Slide

31. My Problem
    def user_profile(request, username):!
    user = request.user!
    if user.is_authenticated():!
    if user.username == username:!
    # Show personal page!
    else:!
    # Show public page!
    else:!
    # Show page for anonymous user
    

    View Slide

32. View Slide

33. Descriptive Boolean
    # is + adjective = method!
    user.is_authenticated()!
    !
    !
    # No!!
    user.is_active!
    !
    # Clearly a noun.!
    user.activeness
    

    View Slide

34. Watch Out
    # is + noun = variable?!
    >>> user.is_staff!
    True!
    !
    # But...!
    >>> '1'.isdigit!
    object at 0x106fa63a0>
    

    View Slide

35. View Slide

36. My Current Solution
    # is + anything = method!
    user.is_authenticated()!
    !
    !
    # WRONG!
    method.is_action = True!
    !
    # Considered correct (but ugly)!
    method.action_flag = True!
    !
    # Maybe use something else?!
    method.action_info = None
    

    View Slide

37. Python lacked
    booleans until 2.2.1
    Maybe we can get away with it.
    

    View Slide

38. Similarly Problematic
    # Makes more sense being a variable!
    request.url!
    !
    # Obviously needs processing. Okay.!
    document.md5()!
    !
    # ???!
    rectangle.left!
    rectangle.center
    

    View Slide

39. No Perfect Solution
    # Parentheses do not matter in Ruby!
    user.authenticated?!
    !
    # But things can get funky quickly!
    proc_obj = proc { user.authenticated? }!
    proc_obj.call!
    !
    # Python can be inconvenient!
    user.is_authenticated()!
    !
    # But obvious things stay obvious!
    func = user.is_authenticated!
    func()
    

    View Slide

40. FIRE QUESTIONS
    

    View Slide