[Baypiggies] December's Talk: Introducing Type Annotations for Python

Jeff Fischer jeffrey.fischer at gmail.com
Mon Dec 5 12:16:25 EST 2016

We have another great talk this month! It will be held a week earlier than
usual on Thursday December 15 at 7 pm. It will be at the same place as last

LinkedIn, Yosemite Room
605 W. Maude Ave, Sunnyvale, CA

*Speakers:* Guido van Rossum, Greg Price, and David Fisher

Dropbox has several million lines of production code written in Python 2.7.
As a first step towards migrating to Python 3, as well as to generally make
our code more navigable, we are annotating our code with type annotations
using the PEP 484 standard and type-checking the annotated code with mypy.
In this talk we will discuss lessons learned and show how you too can start
type-checking your legacy Python 2.7 code, one file at a time. We will also
describe some of the many improvements we’ve made to mypy in the process,
as well as some other tools that come in handy.

Mypy is an open-source type-checker for Python. It was originally created
by one of the speakers, Jukka Lehtosalo, in support of his PhD thesis,
before he joined Dropbox. Mypy supports the PEP 484 standard for gradual
typing in Python. It supports Python 3.2 and higher, as well as Python 2.7
(using function signatures in type comments, per a recent update to PEP

*Speaker Bios*


Guido van Rossum is the author of the Python programming language. He
continues to serve as the "Benevolent Dictator For Life" (BDFL), meaning
that he continues to oversee the Python development process, making
decisions where necessary. He is currently employed by Dropbox.


Jukka Lehtosalo created mypy, an optional static type checker for Python,
while working on his PhD at the University of Cambridge. He currently works
at Dropbox and continues to lead the development of mypy. (Based in UK and
may not be able to attend)


Greg Price is an engineer at Dropbox. Previously he worked at Quora and
helped Ksplice make rebooting obsolete.


David Fisher works full time on mypy (the PEP 484 static type checker) at
Dropbox. He enjoys learning esoteric languages in his spare time.


If you plan to attend, please RSVP at
https://www.meetup.com/BAyPIGgies/events/232817503/. That will help us plan
for the number of chairs and amount of food.

See you there!
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