8 ms·

Flask: a micro web framework for Python

114 points by iamelgringo 17y ago

lbolognini 17y ago
What's the advantage over CherryPy? And furthermore why bother since there's Django that is not any more complicated than your homegrown framework?
simonw 17y ago
Some really interesting ideas here, especially coming at it from a Django background. Flask embraces thread locals - Django tends to pretend they aren't necessary at the user level, even though there are a few of them lurking in the core framework. Flask's request object is thread-safe global, and Flask encourages you to put your own per-request global instances (such as a database connection which is opened at the beginning of the request and closed at the end) on the special flask.g object. I've always disliked this kind of approach because it makes it hard to run your code outside of the context of a web request (e.g. in a cron script), but Flask deals with that by providing a clever test_request_context method: from flask import request with app.test_request_context('/hello', method='POST'): # now you can do something with the request until the # end of the with block, such as basic assertions: assert request.path == '/hello' assert request.method == 'POST' Using the with statement here is very smart - Flask seems to get a lot of mileage out of both context managers and decorators. I'm looking forward to seeing how Flask shapes up - it feels like a very modern attempt at a Python micro-framework, with some pleasantly unconventional ideas.
- jokull 17y ago
  Armin has stated that he thinks that declaring URL routes with decorators is a bad idea. Has he warmed up to it or decided it bearable being a minimal framework? I think they are a bad idea. I love urls.py being kind of a TOC for your application. Apart from that I can see a lot of good ideas in here. Solid template and HTTP layers, signed cookies, avoiding the ORM, short lived messaging, proper __html__, simplistic URL reversal. I love the simple request object API (args, form, files). I can see additional libraries around this core. High level forms library at least.
  - zeemonkee 17y ago
    You don't have to use decorators (they cause issues with circular dependencies as well, making it difficult to break up your views module). There is an add_url_rule method you can use to register views. An ORM is tangental to Flask - there is some docs on how to use with SQLAlchemy (which also suggests WTForms for validation) but it's ORM/DB neutral, which is a good idea. However I'm warming to the idea of avoiding an ORM completely in future projects - just use a thin layer around MySQLdb or DB of choice, like tornado.database or SQLAlchemy's query API.
samratjp 17y ago
Could this be Python's Sinatra?
- 10ren 17y ago
  Isn't web.py already Python's Sinatra? examples here: http://webpy.org/ http://webpy.org/ http://sinatrarb.com/ http://sinatrarb.com/ (I really want to know - it seems very similar to Sinatra to me. What are the differences?).
  - telemachos 17y ago
    Or itty: http://github.com/toastdriven/itty http://github.com/toastdriven/itty Examples of mini-frameworks in various languages: http://gist.github.com/353559 http://gist.github.com/353559
    - igorgue 17y ago
      Or Bottle: http://bottle.paws.de/ http://bottle.paws.de/
  - RyanMcGreal 17y ago
    I'm not experienced with Sinatra, but web.py is a really elegant little framework. It gives you what you need and then gets out of the way. It's also RESTful and gets its HTTP status codes right.
paulsmith 17y ago
If anyone is trying to follow along with the Quickstart, a simple virtualenv + easy_install Flask didn't work for me -- I needed to install Werkzeug tip (easy_install Werkzeug==dev) and install Jinja2 from tip as well (hg clone http://dev.pocoo.org/hg/jinja2-main http://dev.pocoo.org/hg/jinja2-main jinja2).
chairface 17y ago
I think this was an April Fool's joke: http://lucumr.pocoo.org/2010/4/3/april-1st-post-mortem http://lucumr.pocoo.org/2010/4/3/april-1st-post-mortem edit: In response to the downvotes - it appears that it was an April Fool's joke, but because of the response he got, Armin decided to try it out for real. Yeesh.
sumeeta 17y ago
Since it’s by the same author, this is probably inspired by or related to Armin’s April Fools’ Python micro web framework: Denied: Python Micro-Framework (http://news.ycombinator.com/item?id=1237412 http://news.ycombinator.com/item?id=1237412) April 1st Post Mortem (http://news.ycombinator.com/item?id=1239438 http://news.ycombinator.com/item?id=1239438)
xox 17y ago
Will it work on Google App Engine?
- samratjp 17y ago
  Apparently, http://flask.pocoo.org/deploying.html#cgi http://flask.pocoo.org/deploying.html#cgi
buster 17y ago
Also: Python web "framework" in 705 loc: http://github.com/breily/juno http://github.com/breily/juno
tocomment 17y ago
Is this better than bottle?
digispaghetti 17y ago
Reading this the documentation is really easy to read and understand. Doesn't seem to have the restrictions of Django, you could build small distributed apps that communicate over sockets or REST. Would also hope to see good support with document databases like mongodb.
aneth 17y ago
Not that Python needs more web frameworks (http://wiki.python.org/moin/WebFrameworks http://wiki.python.org/moin/WebFrameworks), but it's good to see Python use its new poor-man's equivalent to Ruby's block syntax.
- bretthoerner 17y ago
  Which equivalent are you speaking of?
  - aneth 17y ago
    The 'with' syntax, which only allows execution of code on entrance and exit - no nearly as flexible as Ruby blocks. (I'm not a Python hater, but I do like Ruby blocks.)
mkramlich 17y ago
Not addressing Flask directly but the article made me think of something about small web frameworks. It strikes me as easier to come up with a new "big" web framework than it is with a new small one. Because after a certain point, its hard to come up with a framework where a Hello World web app can be expressed with any fewer lines of code. It's always possible to make a more verbose web app, it may be impossible past a certain point to make one more concise. Perhaps Flash's angle could be not to shrink the minimum LOC needed, but to deliver more features per app LOC.
deleted 17y ago
[deleted]

114 points by iamelgringo 17y ago

What's the advantage over CherryPy? And furthermore why bother since there's Django that is not any more complicated than your homegrown framework?

simonw 17y ago

Some really interesting ideas here, especially coming at it from a Django background. Flask embraces thread locals - Django tends to pretend they aren't necessary at the user level, even though there are a few of them lurking in the core framework. Flask's request object is thread-safe global, and Flask encourages you to put your own per-request global instances (such as a database connection which is opened at the beginning of the request and closed at the end) on the special flask.g object. I've always disliked this kind of approach because it makes it hard to run your code outside of the context of a web request (e.g. in a cron script), but Flask deals with that by providing a clever test_request_context method: from flask import request with app.test_request_context('/hello', method='POST'): # now you can do something with the request until the # end of the with block, such as basic assertions: assert request.path == '/hello' assert request.method == 'POST' Using the with statement here is very smart - Flask seems to get a lot of mileage out of both context managers and decorators. I'm looking forward to seeing how Flask shapes up - it feels like a very modern attempt at a Python micro-framework, with some pleasantly unconventional ideas.

jokull 17y ago
Armin has stated that he thinks that declaring URL routes with decorators is a bad idea. Has he warmed up to it or decided it bearable being a minimal framework? I think they are a bad idea. I love urls.py being kind of a TOC for your application. Apart from that I can see a lot of good ideas in here. Solid template and HTTP layers, signed cookies, avoiding the ORM, short lived messaging, proper __html__, simplistic URL reversal. I love the simple request object API (args, form, files). I can see additional libraries around this core. High level forms library at least.
- zeemonkee 17y ago
  You don't have to use decorators (they cause issues with circular dependencies as well, making it difficult to break up your views module). There is an add_url_rule method you can use to register views. An ORM is tangental to Flask - there is some docs on how to use with SQLAlchemy (which also suggests WTForms for validation) but it's ORM/DB neutral, which is a good idea. However I'm warming to the idea of avoiding an ORM completely in future projects - just use a thin layer around MySQLdb or DB of choice, like tornado.database or SQLAlchemy's query API.

samratjp 17y ago

Could this be Python's Sinatra?

10ren 17y ago
Isn't web.py already Python's Sinatra? examples here: http://webpy.org/ http://webpy.org/ http://sinatrarb.com/ http://sinatrarb.com/ (I really want to know - it seems very similar to Sinatra to me. What are the differences?).
- telemachos 17y ago
  Or itty: http://github.com/toastdriven/itty http://github.com/toastdriven/itty Examples of mini-frameworks in various languages: http://gist.github.com/353559 http://gist.github.com/353559
  - igorgue 17y ago
    Or Bottle: http://bottle.paws.de/ http://bottle.paws.de/
- RyanMcGreal 17y ago
  I'm not experienced with Sinatra, but web.py is a really elegant little framework. It gives you what you need and then gets out of the way. It's also RESTful and gets its HTTP status codes right.

paulsmith 17y ago

If anyone is trying to follow along with the Quickstart, a simple virtualenv + easy_install Flask didn't work for me -- I needed to install Werkzeug tip (easy_install Werkzeug==dev) and install Jinja2 from tip as well (hg clone http://dev.pocoo.org/hg/jinja2-main http://dev.pocoo.org/hg/jinja2-main jinja2).

chairface 17y ago

I think this was an April Fool's joke: http://lucumr.pocoo.org/2010/4/3/april-1st-post-mortem http://lucumr.pocoo.org/2010/4/3/april-1st-post-mortem edit: In response to the downvotes - it appears that it was an April Fool's joke, but because of the response he got, Armin decided to try it out for real. Yeesh.

sumeeta 17y ago

Since it’s by the same author, this is probably inspired by or related to Armin’s April Fools’ Python micro web framework: Denied: Python Micro-Framework (http://news.ycombinator.com/item?id=1237412 http://news.ycombinator.com/item?id=1237412) April 1st Post Mortem (http://news.ycombinator.com/item?id=1239438 http://news.ycombinator.com/item?id=1239438)

xox 17y ago

Will it work on Google App Engine?

samratjp 17y ago
Apparently, http://flask.pocoo.org/deploying.html#cgi http://flask.pocoo.org/deploying.html#cgi

buster 17y ago

Also: Python web "framework" in 705 loc: http://github.com/breily/juno http://github.com/breily/juno

tocomment 17y ago

Is this better than bottle?

digispaghetti 17y ago

Reading this the documentation is really easy to read and understand. Doesn't seem to have the restrictions of Django, you could build small distributed apps that communicate over sockets or REST. Would also hope to see good support with document databases like mongodb.

aneth 17y ago

Not that Python needs more web frameworks (http://wiki.python.org/moin/WebFrameworks http://wiki.python.org/moin/WebFrameworks), but it's good to see Python use its new poor-man's equivalent to Ruby's block syntax.

bretthoerner 17y ago
Which equivalent are you speaking of?
- aneth 17y ago
  The 'with' syntax, which only allows execution of code on entrance and exit - no nearly as flexible as Ruby blocks. (I'm not a Python hater, but I do like Ruby blocks.)

mkramlich 17y ago

Not addressing Flask directly but the article made me think of something about small web frameworks. It strikes me as easier to come up with a new "big" web framework than it is with a new small one. Because after a certain point, its hard to come up with a framework where a Hello World web app can be expressed with any fewer lines of code. It's always possible to make a more verbose web app, it may be impossible past a certain point to make one more concise. Perhaps Flash's angle could be not to shrink the minimum LOC needed, but to deliver more features per app LOC.

deleted 17y ago

[deleted]