利用Python Flask构建Web网站

jieforest · 发表于 2012-10-19 13:59

In our module’s __init__.py:

import os
# ...
env = os.environ.get('EXAMPLE_ENV', 'prod')
app.config.from_object('example.settings.%sConfig' % env.capitalize())
app.config['ENV'] = env

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jieforest · 发表于 2012-10-19 14:00

Assets

With the rise of rich frontends and of alternative syntaxes to css and javascript, assets manaegement has become an important aspect of web apps.

We’ll once again use a great extension, Flask-Assets, which is a wrapper for the webassets python library.

$ pip install Flask-Assets

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jieforest · 发表于 2012-10-19 14:00

I store my assets file in static/, organizing them inside a css/, js/ and vendor/ folders. Below you can see that I’ve added jquery and bootstrap in the vendor dir.

example/
static/
css/
layout.less
js/
main.js
vendor/
bootstrap/
css/
bootstrap.css
js/
bootstrap.min.js
jquery/
jquery-1.7.2.min.js

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jieforest · 发表于 2012-10-20 09:26

With webassets, files are grouped as bundles. Each bundle can have custom filters (eg: transform less files to css). I define my bundles inside an assets.py file:

from flask_assets import Bundle
common_css = Bundle(
'vendor/bootstrap/css/bootstrap.css',
Bundle(
'css/layout.less',
filters='less'
),
filters='cssmin', output='public/css/common.css')
common_js = Bundle(
'vendor/jquery/jquery-1.7.2.min.js',
'vendor/bootstrap/js/bootstrap.min.js',
Bundle(
'js/main.js',
filters='closure_js'
),
output='public/js/common.js')

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jieforest · 发表于 2012-10-20 09:26

Here I have defined 2 bundles, one for css files and one for js files. I’ve also use nested bundles to apply specific filters to some files.

To include the bundles in our pages, webassets provides some jinja2 helpers (which we should add tolayout.html):

{% assets "common_css" %}
<link rel="stylesheet" type="text/css" href="{{ ASSET_URL }}" />
{% endassets %}
{% assets "common_js" %}
<script type="text/javascript" src="{{ ASSET_URL }}"></script>
{% endassets %}

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jieforest · 发表于 2012-10-20 09:26

Now we’ll need to configure the webassets environment in __init__.py:

from flask_assets import Environment
from webassets.loaders import PythonLoader as PythonAssetsLoader
import assets
# ...
assets_env = Environment(app)
assets_loader = PythonAssetsLoader(assets)
for name, bundle in assets_loader.load_bundles().iteritems():
assets_env.register(name, bundle)

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jieforest · 发表于 2012-10-20 09:27

As you can see, I use webassets’s PythonLoader to load bundles from the assets module and register each bundle into the environment.

You can add ASSETS_DEBUG=True in DevConfig to get debugging info. There are many other configuration parameters listed here. Param names should be prefixed with ASSETS_ and uppercased (eg.Environment.versions becomes ASSETS_VERSIONS).

Finally, the Flask-Assets extension provides some command line utilities that we’ll need to register in the manage.py file:

from flask_assets import ManageAssets
from example import assets_env
# ...
manager.add_command("assets", ManageAssets(assets_env))

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jieforest · 发表于 2012-10-20 09:28

Available commands are listed in webassets documentation but the most important one is rebuild which regenerates all your bundle files:

$ ./manage.py assets rebuild

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Deploying to production

Now that we have a fully working Flask application, we’ll need to deploy it on a production machine. I like to use uWSGI + Nginx + Supervisor for my setup.

Note: this part assumes Ubuntu as your Linux distribution

Nginx acts as the frontend web server and will serve static files. uWSGI acts as the WSGI server which runs our flask app. Finally, I use supervisor to manage processes. I like to use Supervisor instead of init.d scripts as I often have other processes to manage.

$ sudo apt-get install nginx supervisor
$ pip install uwsgi

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