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PyCon: Opening the Flask

Opening the Flask

The talk was by Armin Ronacher, one of the authors of Flask.

Flask started as an elaborate April Fool's joke.

The guys who did Flask did a lot of cool stuff before doing Flask, such as Jinja2.

Flask was originally Jinja2, Werkzeug, and some glue code cleverly embedded in a single file download.

Marketing beats quality.

Originally, they didn't do any testing or any code review. That's changed.

They wanted to restart with good docs and good tests. They documentation and tests are pretty good these days.

The name "Flask" is a play on another framework, "Bottle".

Flask is still based on Werkzeug and Jinja2.

Flask can use Blinker as a signalling system (?).

Flask is about 800 lines of code, 1500 lines of tests, and 200 A4-sized pages of documentation.

There are lots of extensions.

Flask uses decorator-based routes, but there are other options.

Flask supports URL routing as well as URL generation.

Jinja2 uses template inheritance.

They use context locals to make writing apps simper. Armin suggests that you might as well embrace context locals--you'll end up needing them anyway.

Armin is very against import-time side effects.

Flask is in favor of explicit application setup. For Flask, this has occasionally led to circular imports that they had to find workarounds for.

WSGI middleware works with Flask.

Flask has several advantages over Bottle.

You can override various aspects of how Flask works. For instance, you can use the "@app.before_request" and "@app.after_request" decorators.

They make use of lots of extensions.

Flask has a goal of keeping the core very small.

You can use other templating engines if you want, but Jinja2 will always be a dependency just in case any extensions need it.

Documentation matters.

Communication matters. It's very easy to submit issues to Flask. You don't even need to create an account.

It's important to keep committing to projects otherwise the project looks dead.

Consistency matters.

It's important that even the documentation be beautiful.

Flask uses Sphinx for documentation.

Armin didn't have a strong rule of thumb for when you should use Flask vs. Pyramid. Neither the Flask guys nor the Pyramid guys are overly religious about their frameworks.

The audience turnout was about the same for both the Flask and Pyramid talks.

The Flask guys are thinking about redoing the code for reverse routing.

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