[PyCon JP 2026] So You Think You Know Python?

Python is a language full of delightful surprises, if you know where to look. This talk takes you on a guided tour of its most interesting quirks, from easter eggs buried in the standard library, to real-world examples of how the language's gotchas have tripped up even the most seasoned developers.

This talk goes through code, documentation, PEPs, mailing list threads, discussions in issue trackers, webcomics, and other sources to get the answers to the following questions (and more):

- Is midnight falsy?
- Why does `~True` equal -2?
- What is the hash of infinity?
- How many references to xkcd webcomics are in the standard library?
- Why can't raw strings end with an odd number of backslashes?

Transcript

1. So You Think You Know Python? Jordan Duabe Pycon JP, 2026-08-21
2. Agenda • • • Quirks and easter eggs Gotchas and real-world examples Quiz (?)
3. whoami Jordan Duabe Software Engineer at Anaqua me@jduabe.dev @j4ckofalltrades@infosec.exchange Images (cropped) from L to R: Виктор В, CC BY-SA 3.0 — Pedro Szekely from Los Angeles, USA, CC BY-SA 2.0 — Nestek, CC BY-SA 4.0 (all via Wikimedia Commons) First World Metal Problems meme via Know Your Meme — Photos by Jordan Duabe
4. Quirks and easter eggs
5. Finding your Zen
6. PEP 20 – The Zen of Python Abstract Long time Pythoneer Tim Peters succinctly channels the BDFL’s guiding principles for Python’s design into 20 aphorisms, only 19 of which have been written down.
7. Zen of Python
8. Hello world!
9. Hello world!
10. Breakfast of champions
11. Frozen modules
12. Frozen modules
13. PEP 401 – BDFL Retirement Summary The BDFL, having shepherded Python development for 20 years, officially announces his retirement effective immediately (Barry Warsaw aka Uncle Barry aka FLUFL). His official title is now Benevolent Dictator Emeritus Vacationing Indefinitely from the Language (BDEVIL). Guido trains for his lifelong dream of climbing Mount Everest.
14. Not Equals
15. Brace yourselves
16. Look away!
17. Don’t leave me hanging
18. NOT like this
19. To Infinity and NaN
20. 𝜋 thon
21. 𝜋 thon
22. 𝜋 minus
23. XKCD 936 Generate an XKCD-style passphrase: import secrets # On standard Linux systems, use a convenient dictionary file. # Other platforms may need to provide their own word-list. with open('/usr/share/dict/words') as f: words = [word.strip() for word in f] password = ' '.join(secrets.choice(words) for i in range(4))
24. XKCD 2200
25. XKCD 353 >>> import antigravity
26. XKCD 426 >>> from antigravity import geohash
28. Source: https://geohashing.site/geohashing/2008-06-06_-27_153
29. Gotchas and real-world examples
30. Is midnight falsy?
31. TODO add slide
33. Re: Please reconsider the Boolean evaluation of midnight If I had to do it over again I would *definitely* never make a time value "falsy". The datetime module was conceived long ago, when the dangers of falsy objects that weren't clearly trying to be "like numbers" or "like collections" weren't so clear. Today I would argue that times aren't enough "like numbers" to qualify. --Guido van Rossum (python.org/~guido)
34. Without warning
37. Solution
38. is equal
40. toronto.onepeloton.com Source: What a Bug can Teach You about Python by Brad Dettmer
41. The Bug Source: What a Bug can Teach You about Python by Brad Dettmer
42. Buggy code in backend server 257 257 if appointment.time_slot_id is ts.id: time_slot_appointments.append(appointment) Source: What a Bug can Teach You about Python by Brad Dettmer
43. Source: What a Bug can Teach You about Python by Brad Dettmer
44. Quiz jduabe.dev/pyconjp2026-quiz
45. Thank You talks.jduabe.dev/pdf/pycon-jp-2026.pdf
46. Sources • • • • • • • • • https://hub.docker.com/r/j4ckofalltrades/legacy-python https://mail.python.org/pipermail/python-list/1999-June/001951.html https://docs.python.org/3/faq/design.html#why-can-t-raw-strings-r-strings-end-with-a-backslash https://docs.python.org/3/library/secrets.html https://lwn.net/Articles/590299/ https://lwn.net/Articles/590331/ https://sethmlarson.dev/deprecations-via-warnings-dont-work-for-python-libraries https://docs.python.org/3/c-api/long.html#:~:text=CPython,object https://docs.google.com/presentation/d/1mDeGnYlkYEvIuAfEGTyTk-vUaYvALkdqfnuGIRqz0Hs
47. Image credits • "Australia relief map" by Виктор В, CC BY-SA 3.0 (creativecommons.org/licenses/by-sa/3.0). Source: en.wikipedia.org/wiki/File:Australia_relief_map.jpg • "Rottnest Island coastline near Parker Point 01" by Pedro Szekely, CC BY-SA 2.0 (creativecommons.org/licenses/by-sa/2.0). Source: commons.wikimedia.org/wiki/File:Rottnest_Island_coastline_near_Parker_Point_01.jpg • "Quokkas Closeup" by Nestek, CC BY-SA 4.0 (creativecommons.org/licenses/by-sa/4.0). Source: commons.wikimedia.org/wiki/File:Quokkas_Closeup.jpg • "First World Metal Problems" meme, via Know Your Meme. Source: knowyourmeme.com/photos/426359-first-world-metal-problems