Talking 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.

1. A Python Æsthetic

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

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

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

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

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

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

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

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

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

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

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

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!

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!

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

16. [P]racticality beats purity.

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

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

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

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

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

22. Problem of Pluralization
>>> connections!
[<SQLConnection at 0xb72ff4d8>,!
<SQLConnection at 0xb72ff4d0>,!
<SQLConnection at 0xb72ff4f0>]!
!
>>> connections!
{'master': <SQLConnection at 0xb72ff4d8>,!
'backup': <SQLConnection at 0xb72ff4f0>}

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

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

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

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

27. My Problem

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

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

30. My Problem
>>> user.is_authenticated!
<bound method User.is_authenticated of
<User: admin>>

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

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

34. Watch Out
# is + noun = variable?!
>>> user.is_staff!
True!
!
# But...!
>>> '1'.isdigit!
<built-in method isdigit of str
object at 0x106fa63a0>

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

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

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

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()

40. FIRE QUESTIONS