If you're looking for a nice Python web framework, try Pylons/Pyramid
Pylons is loosely coupled. Not Django.
Django is not bad and it certainly makes it easier for 99% of projects out there (CMS style). But for the 1% it's a pain.
If you want to use an ORM, or have database backed sessions, or user logins, you need to write all that yourself. For example: http://flask.pocoo.org/docs/patterns/sqlalchemy/
Depending on what you're doing, that might be a good thing - but I find writing things which are already included in Django pretty annoying.
I said everything you need to make web apps in Python, and I stand by that. Maybe it doesn't have an ORM or user account management, but for my purposes, it's great for small apps.
However, the Extensions library [-1] (which is not strictly speaking part of Flask) provides quite a lot of functionality - apart from your referred SQLAlchemy (which does the job well in our backend), there's a nice API generation factory [0] [1] and other neat stuff. For quite a lot of intents/purposes, flask extensions will do the job. But in the end of course it is a microframework. (From limited personal experience, a very neat general-purpose microframework nevertheless!)
[-1] http://flask.pocoo.org/extensions/ [0] [1] A particularly sexy example that simply uses models from SQLAlchemy (from the quickstart in [0]): manager.create_api(Person, methods=['GET', 'POST', 'DELETE']) manager.create_api(Computer, methods=['GET'])
where Computer and Person are DB models easily defined with the help of SQLalch.
(This is not to counter (there isn't anything to be countered, just providing links / luring people..)
Flask is not a "micro" microframework per se.
It provides a thin facade over werkzeug - which is anything but lightweight or micro.
Another Flask fan here. If Armin says Flask is micro, and other frameworks which aren't considered micro are far larger than Flask, what makes Flask not a micro framework?
The extensions were mentioned; User logins for example are just a "pip install Flask-Login" and "from flaskext.login import whatever" away. I had reason to roll my own, ~100 simple lines that were easily plugged.
There are pros and cons, neither is "better", the right tradeoff depends on what you're making.
For example, Flask-Login (https://github.com/maxcountryman/flask-login/blob/master/fla...) imports md5 and sha1 - not a very good sign. How do I make it use something sane? Well, there's Flask-Bcrypt, which provides bcrypt hashing... except that it makes no mention of Flask-Login or how to integrate it. Flask-Login also doesn't mention Flask-Bcrypt.
So... you're back to hacking on or digging into Flask-Login to figure out how it works and making it use Bcrypt or some other hashing algorithm.
Wait - I just realised that Flask-Login doesn't handle storing user data or models, or checking passwords, just logging them in. So what do I need for that? Is that Flask-Principal? And just WTH is an IdentityContext, anyway?
An IdentityContext is the context of a certain identity
against a certain Permission. It can be used as a
context manager, or a decorator.
Functionality added usually doesn't break what currently works (except maybe for bugs fixed)
I like the mapping of a resource to class and method names to class method.s I am not sure I like Flask's method handling and having to do if ... elif .... else (maybe I just found some bad example, so please correct me).
Also url dispatching at the top makes it easier to understand what's going on rather than having it spread to each of the decorators somehow.
Django isn't loosely coupled by default, but it can be used in a relatively loosely coupled way. E.g. you can easily use your own SQL and templating engine. Yes you can't just hot swap in a new web framework without rewriting the core app code, but that's the case with every framework.