On Tue, Jun 20, 2017 at 8:06 AM, Kushal Das <mail@xxxxxxxxxxxx> wrote: > Hi everyone, > > RFC: Enable type annotations and Mypy checks on Python projects in Fedora Infrastructure > > > We have many Python applications under Fedora Infrastructure, and we > also on a path to move to the Python3 world. I am proposing the > following changes for our Python applications: > > * Add type annotations in any new code we write. > * Add type annotations in code we change > * Enable Mypy checks for every pull requests and commits in CI. > * During Flock we try to enable type annotations in our favorite Python applications. > > > ## What is Type Annotation > > This is a feature of Python3, also backported to the Python2 world using > the python2-typing module. Type annotations or type hints are purely for > external type checking tools, they do not affect the Python interpreter > anyway. PEP-484 discusses more on the type hints [1]. > > ## Example (which works in both Python2 and Python3) > > def add(a, b): > # type: (int, int) -> int > "Adds two numbers" > return a + b > > > > ## What is Mypy? > > Mypy [2] is an open source type checking tool, most of the developers > are in Dropbox. Mypy can be used on a codebase gradually, means we don't > have to add all the type information in one go. We can slowly keep > improving the type annotations. > > ## What are benefits of enable type annotations and Mypy? > > > ### Readability of the code > > Because of the checks, we will always have right data types mentioned, > which increases the readability of the code a lot for any future > maintainer. > > ### Finding actual logical bugs > > There are times when we have functions which generally returns a > boolean, but it some corner cases, maybe it returns an empty string or > None value. These may cause runtime errors. Using Mypy on your codebase > improves the chances of finding any such issue in the development cycle > only. > > ### Refactoring becomes easier > > As the tool itself checks for all of the API use cases, refactoring > larger codebases will be easier with Mypy. > > > ## Which are the few big projects using Mypy? > > Dropbox has around 700K lines of Python code, and Zulip project has > around 100K of Python with type information. They also have an excellent > blog post at [3]. > > [1] https://www.python.org/dev/peps/pep-0484/ > [2] http://mypy.readthedocs.io/en/latest/ > [3] http://blog.zulip.org/2016/10/13/static-types-in-python-oh-mypy/ > FWIW +1 from me I'm a big fan of mypy and type annotations. I'm currently using type annotations in my custom ansible modules in the releng-automation project space. -AdamM > Kushal > -- > Fedora Cloud Engineer > CPython Core Developer > https://kushaldas.in > https://dgplug.org > _______________________________________________ > infrastructure mailing list -- infrastructure@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe send an email to infrastructure-leave@xxxxxxxxxxxxxxxxxxxxxxx _______________________________________________ infrastructure mailing list -- infrastructure@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to infrastructure-leave@xxxxxxxxxxxxxxxxxxxxxxx
