This tutorial introduces you to the concepts and features of the Bottle web framework and covers basic and advanced topics alike. You can read it from start to end, or use it as a reference later on. The automatically generated API Reference may be interesting for you, too. It covers more details, but explains less than this tutorial. Solutions for the most common questions can be found in our Recipes collection or on the Frequently Asked Questions page. If you need any help, join our mailing list or visit us in our IRC channel.
Bottle does not depend on any external libraries. You can just download bottle.py into your project directory and start coding:
$ wget http://bottlepy.org/bottle.py
This will get you the latest development snapshot that includes all the new features. If you prefer a more stable environment, you should stick with the stable releases. These are available on PyPi and can be installed via pip (recommended), easy_install or your package manager:
$ sudo pip install bottle # recommended
$ sudo easy_install bottle # alternative without pip
$ sudo apt-get install python-bottle # works for debian, ubuntu, ...
Either way, you’ll need Python 2.5 or newer (including 3.x) to run bottle applications. If you do not have permissions to install packages system-wide or simply don’t want to, create a virtualenv first:
$ virtualenv develop # Create virtual environment
$ source develop/bin/activate # Change default python to virtual one
(develop)$ pip install -U bottle # Install bottle to virtual environment
Or, if virtualenv is not installed on your system:
$ wget https://raw.github.com/pypa/virtualenv/master/virtualenv.py
$ python virtualenv.py develop # Create virtual environment
$ source develop/bin/activate # Change default python to virtual one
(develop)$ pip install -U bottle # Install bottle to virtual environment
This tutorial assumes you have Bottle either installed or copied into your project directory. Let’s start with a very basic “Hello World” example:
from bottle import route, run
@route('/hello')
def hello():
return "Hello World!"
run(host='localhost', port=8080, debug=True)
This is it. Run this script, visit http://localhost:8080/hello and you will see “Hello World!” in your browser. Here is how it works:
The route() decorator binds a piece of code to an URL path. In this case, we link the /hello URL to the hello() function. This is called a route (hence the decorator name) and is the most important concept of this framework. You can define as many routes as you want. Whenever a browser requests an URL, the associated function is called and the return value is sent back to the browser. Its as simple as that.
The run() call in the last line starts a built-in development server. It runs on localhost port 8080 and serves requests until you hit Control-c. You can switch the server backend later, but for now a development server is all we need. It requires no setup at all and is an incredibly painless way to get your application up and running for local tests.
The Debug Mode is very helpful during early development, but should be switched off for public applications. Keep that in mind.
Of course this is a very simple example, but it shows the basic concept of how applications are built with Bottle. Continue reading and you’ll see what else is possible.
For the sake of simplicity, most examples in this tutorial use a module-level route() decorator to define routes. This adds routes to a global “default application”, an instance of Bottle that is automatically created the first time you call route(). Several other module-level decorators and functions relate to this default application, but if you prefer a more object oriented approach and don’t mind the extra typing, you can create a separate application object and use that instead of the global one:
from bottle import Bottle, run, template
app = Bottle()
@app.route('/hello')
def hello():
return "Hello World!"
run(app, host='localhost', port=8080)
The object-oriented approach is further described in the Default Application section. Just keep in mind that you have a choice.
In the last chapter we built a very simple web application with only a single route. Here is the routing part of the “Hello World” example again:
@route('/hello')
def hello():
return "Hello World!"
The route() decorator links an URL path to a callback function, and adds a new route to the default application. An application with just one route is kind of boring, though. Let’s add some more:
@route('/')
@route('/hello/<name>')
def greet(name='Stranger'):
return template('Hello {{name}}, how are you?', name=name)
This example demonstrates two things: You can bind more than one route to a single callback, and you can add wildcards to URLs and access them via keyword arguments.
Routes that contain wildcards are called dynamic routes (as opposed to static routes) and match more than one URL at the same time. A simple wildcard consists of a name enclosed in angle brackets (e.g. <name>) and accepts one or more characters up to the next slash (/). For example, the route /hello/<name> accepts requests for /hello/alice as well as /hello/bob, but not for /hello, /hello/ or /hello/mr/smith.
Each wildcard passes the covered part of the URL as a keyword argument to the request callback. You can use them right away and implement RESTful, nice-looking and meaningful URLs with ease. Here are some other examples along with the URLs they’d match:
@route('/wiki/<pagename>') # matches /wiki/Learning_Python
def show_wiki_page(pagename):
...
@route('/<action>/<user>') # matches /follow/defnull
def user_api(action, user):
...
New in version 0.10.
Filters are used to define more specific wildcards, and/or transform the covered part of the URL before it is passed to the callback. A filtered wildcard is declared as <name:filter> or <name:filter:config>. The syntax for the optional config part depends on the filter used.
The following filters are implemented by default and more may be added:
:int matches (signed) digits only and converts the value to integer.
:float similar to :int but for decimal numbers.
:path matches all characters including the slash character in a non-greedy way and can be used to match more than one path segment.
:re allows you to specify a custom regular expression in the config field. The matched value is not modified.
Let’s have a look at some practical examples:
@route('/object/<id:int>')
def callback(id):
assert isinstance(id, int)
@route('/show/<name:re:[a-z]+>')
def callback(name):
assert name.isalpha()
@route('/static/<path:path>')
def callback(path):
return static_file(path, ...)
You can add your own filters as well. See Routing for details.
Changed in version 0.10.
The new rule syntax was introduced in Bottle 0.10 to simplify some common use cases, but the old syntax still works and you can find a lot of code examples still using it. The differences are best described by example:
Old Syntax |
New Syntax |
|---|---|
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Try to avoid the old syntax in future projects if you can. It is not currently deprecated, but will be eventually.
The HTTP protocol defines several request methods (sometimes referred to as “verbs”) for different tasks. GET is the default for all routes with no other method specified. These routes will match GET requests only. To handle other methods such as POST, PUT or DELETE, add a method keyword argument to the route() decorator or use one of the four alternative decorators: get(), post(), put() or delete().
The POST method is commonly used for HTML form submission. This example shows how to handle a login form using POST:
from bottle import get, post, request
@get('/login') # or @route('/login')
def login_form():
return '''<form method="POST" action="/login">
<input name="name" type="text" />
<input name="password" type="password" />
<input type="submit" />
</form>'''
@post('/login') # or @route('/login', method='POST')
def login_submit():
name = request.forms.get('name')
password = request.forms.get('password')
if check_login(name, password):
return "<p>Your login was correct</p>"
else:
return "<p>Login failed</p>"
In this example the /login URL is linked to two distinct callbacks, one for GET requests and another for POST requests. The first one displays a HTML form to the user. The second callback is invoked on a form submission and checks the login credentials the user entered into the form. The use of Request.forms is further described in the Request Data section.
Special Methods: HEAD and ANY
The HEAD method is used to ask for the response identical to the one that would correspond to a GET request, but without the response body. This is useful for retrieving meta-information about a resource without having to download the entire document. Bottle handles these requests automatically by falling back to the corresponding GET route and cutting off the request body, if present. You don’t have to specify any HEAD routes yourself.
Additionally, the non-standard ANY method works as a low priority fallback: Routes that listen to ANY will match requests regardless of their HTTP method but only if no other more specific route is defined. This is helpful for proxy-routes that redirect requests to more specific sub-applications.
To sum it up: HEAD requests fall back to GET routes and all requests fall back to ANY routes, but only if there is no matching route for the original request method. It’s as simple as that.
Static files such as images or CSS files are not served automatically. You have to add a route and a callback to control which files get served and where to find them:
from bottle import static_file
@route('/static/<filename>')
def server_static(filename):
return static_file(filename, root='/path/to/your/static/files')
The static_file() function is a helper to serve files in a safe and convenient way (see Static Files). This example is limited to files directly within the /path/to/your/static/files directory because the <filename> wildcard won’t match a path with a slash in it. To serve files in subdirectories, change the wildcard to use the path filter:
@route('/static/<filepath:path>')
def server_static(filepath):
return static_file(filepath, root='/path/to/your/static/files')
Be careful when specifying a relative root-path such as root='./static/files'. The working directory (./) and the project directory are not always the same.
If anything goes wrong, Bottle displays an informative but fairly plain error page. You can override the default for a specific HTTP status code with the error() decorator:
from bottle import error
@error(404)
def error404(error):
return 'Nothing here, sorry'
From now on, 404 File not Found errors will display a custom error page to the user. The only parameter passed to the error-handler is an instance of HTTPError. Apart from that, an error-handler is quite similar to a regular request callback. You can read from request, write to response and return any supported data-type except for HTTPError instances.
Error handlers are used only if your application returns or raises an HTTPError exception (abort() does just that). Changing Request.status or returning HTTPResponse won’t trigger the error handler.
In pure WSGI, the range of types you may return from your application is very limited. Applications must return an iterable yielding byte strings. You may return a string (because strings are iterable) but this causes most servers to transmit your content char by char. Unicode strings are not allowed at all. This is not very practical.
Bottle is much more flexible and supports a wide range of types. It even adds a Content-Length header if possible and encodes unicode automatically, so you don’t have to. What follows is a list of data types you may return from your application callbacks and a short description of how these are handled by the framework:
As mentioned above, Python dictionaries (or subclasses thereof) are automatically transformed into JSON strings and returned to the browser with the Content-Type header set to application/json. This makes it easy to implement json-based APIs. Data formats other than json are supported too. See the tutorial-output-filter to learn more.
False, None or other non-true values:These produce an empty output with the Content-Length header set to 0.
Unicode strings (or iterables yielding unicode strings) are automatically encoded with the codec specified in the Content-Type header (utf8 by default) and then treated as normal byte strings (see below).
Bottle returns strings as a whole (instead of iterating over each char) and adds a Content-Length header based on the string length. Lists of byte strings are joined first. Other iterables yielding byte strings are not joined because they may grow too big to fit into memory. The Content-Length header is not set in this case.
HTTPError or HTTPResponseReturning these has the same effect as when raising them as an exception. In case of an HTTPError, the error handler is applied. See Error Pages for details.
Everything that has a .read() method is treated as a file or file-like object and passed to the wsgi.file_wrapper callable defined by the WSGI server framework. Some WSGI server implementations can make use of optimized system calls (sendfile) to transmit files more efficiently. In other cases this just iterates over chunks that fit into memory. Optional headers such as Content-Length or Content-Type are not set automatically. Use send_file() if possible. See Static Files for details.
You are allowed to use yield within your callbacks or return an iterable, as long as the iterable yields byte strings, unicode strings, HTTPError or HTTPResponse instances. Nested iterables are not supported, sorry. Please note that the HTTP status code and the headers are sent to the browser as soon as the iterable yields its first non-empty value. Changing these later has no effect.
The ordering of this list is significant. You may for example return a subclass of str with a read() method. It is still treated as a string instead of a file, because strings are handled first.
Changing the Default Encoding
Bottle uses the charset parameter of the Content-Type header to decide how to encode unicode strings. This header defaults to text/html; charset=UTF8 and can be changed using the Response.content_type attribute or by setting the Response.charset attribute directly. (The Response object is described in the section The Response Object.)
from bottle import response
@route('/iso')
def get_iso():
response.charset = 'ISO-8859-15'
return u'This will be sent with ISO-8859-15 encoding.'
@route('/latin9')
def get_latin():
response.content_type = 'text/html; charset=latin9'
return u'ISO-8859-15 is also known as latin9.'
In some rare cases the Python encoding names differ from the names supported by the HTTP specification. Then, you have to do both: first set the Response.content_type header (which is sent to the client unchanged) and then set the Response.charset attribute (which is used to encode unicode).
You can directly return file objects, but static_file() is the recommended way to serve static files. It automatically guesses a mime-type, adds a Last-Modified header, restricts paths to a root directory for security reasons and generates appropriate error responses (401 on permission errors, 404 on missing files). It even supports the If-Modified-Since header and eventually generates a 304 Not Modified response. You can pass a custom MIME type to disable guessing.
from bottle import static_file
@route('/images/<filename:re:.*\.png>#')
def send_image(filename):
return static_file(filename, root='/path/to/image/files', mimetype='image/png')
@route('/static/<filename:path>')
def send_static(filename):
return static_file(filename, root='/path/to/static/files')
You can raise the return value of static_file() as an exception if you really need to.
Forced Download
Most browsers try to open downloaded files if the MIME type is known and assigned to an application (e.g. PDF files). If this is not what you want, you can force a download dialog and even suggest a filename to the user:
@route('/download/<filename:path>')
def download(filename):
return static_file(filename, root='/path/to/static/files', download=filename)
If the download parameter is just True, the original filename is used.
The abort() function is a shortcut for generating HTTP error pages.
from bottle import route, abort
@route('/restricted')
def restricted():
abort(401, "Sorry, access denied.")
To redirect a client to a different URL, you can send a 303 See Other response with the Location header set to the new URL. redirect() does that for you:
from bottle import redirect
@route('/wrong/url')
def wrong():
redirect("/right/url")
You may provide a different HTTP status code as a second parameter.
Note
Both functions will interrupt your callback code by raising an HTTPError exception.
Other Exceptions
All exceptions other than HTTPResponse or HTTPError will result in a 500 Internal Server Error response, so they won’t crash your WSGI server. You can turn off this behavior to handle exceptions in your middleware by setting bottle.app().catchall to False.
Response Object¶Response metadata such as the HTTP status code, response headers and cookies are stored in an object called response up to the point where they are transmitted to the browser. You can manipulate these metadata directly or use the predefined helper methods to do so. The full API and feature list is described in the API section (see Response), but the most common use cases and features are covered here, too.
Status Code
The HTTP status code controls the behavior of the browser and defaults to 200 OK. In most scenarios you won’t need to set the Response.status attribute manually, but use the abort() helper or return an HTTPResponse instance with the appropriate status code. Any integer is allowed, but codes other than the ones defined by the HTTP specification will only confuse the browser and break standards.
Response Header
Response headers such as Cache-Control or Location are defined via Response.set_header(). This method takes two parameters, a header name and a value. The name part is case-insensitive:
@route('/wiki/<page>')
def wiki(page):
response.set_header('Content-Language', 'en')
...
Most headers are unique, meaning that only one header per name is send to the client. Some special headers however are allowed to appear more than once in a response. To add an additional header, use Response.add_header() instead of Response.set_header():
response.set_header('Set-Cookie', 'name=value')
response.add_header('Set-Cookie', 'name2=value2')
Please note that this is just an example. If you want to work with cookies, read ahead.
Bottle provides access to HTTP-related metadata such as cookies, headers and POST form data through a global request object. This object always contains information about the current request, as long as it is accessed from within a callback function. This works even in multi-threaded environments where multiple requests are handled at the same time. For details on how a global object can be thread-safe, see contextlocal.
Note
Bottle stores most of the parsed HTTP metadata in FormsDict instances. These behave like normal dictionaries, but have some additional features: All values in the dictionary are available as attributes. These virtual attributes always return a unicode string, even if the value is missing. In that case, the string is empty.
FormsDict is a subclass of MultiDict and can store more than one value per key. The standard dictionary access methods will only return a single value, but the MultiDict.getall() method returns a (possibly empty) list of all values for a specific key.
The full API and feature list is described in the API section (see Request), but the most common use cases and features are covered here, too.
Cookies are stored in BaseRequest.cookies as a FormsDict. The BaseRequest.get_cookie() method allows access to signed cookies as described in a separate section. This example shows a simple cookie-based view counter:
from bottle import route, request, response
@route('/counter')
def counter():
count = int( request.cookies.get('counter', '0') )
count += 1
response.set_cookie('counter', str(count))
return 'You visited this page %d times' % count
All HTTP headers sent by the client (e.g. Referer, Agent or Accept-Language) are stored in a WSGIHeaderDict and accessible through BaseRequest.headers. A WSGIHeaderDict is basically a dictionary with case-insensitive keys:
from bottle import route, request
@route('/is_ajax')
def is_ajax():
if request.headers.get('X-Requested-With') == 'XMLHttpRequest':
return 'This is an AJAX request'
else:
return 'This is a normal request'
The query string (as in /forum?id=1&page=5) is commonly used to transmit a small number of key/value pairs to the server. You can use the BaseRequest.query (a FormsDict) to access these values and the BaseRequest.query_string attribute to get the whole string.
from bottle import route, request, response
@route('/forum')
def display_forum():
forum_id = request.query.id
page = request.query.page or '1'
return 'Forum ID: %s (page %s)' % (forum_id, page)
The request body of POST and PUT requests may contain form data encoded in various formats. The BaseRequest.forms dictionary contains parsed textual form fields, BaseRequest.files stores file uploads and BaseRequest.POST combines both dictionaries into one. All three are FormsDict instances and are created on demand. File uploads are saved as special cgi.FieldStorage objects along with some metadata. Finally, you can access the raw body data as a file-like object via BaseRequest.body.
Here is an example for a simple file upload form:
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="text" name="name" />
<input type="file" name="data" />
</form>
from bottle import route, request
@route('/upload', method='POST')
def do_upload():
name = request.forms.name
data = request.files.data
if name and data and data.file:
raw = data.file.read() # This is dangerous for big files
filename = data.filename
return "Hello %s! You uploaded %s (%d bytes)." % (name, filename, len(raw))
return "You missed a field."
In Python 2 all keys and values are byte-strings. If you need unicode, you can call FormsDict.getunicode() or fetch values via attribute access. Both methods try to decode the string (default: utf8) and return an empty string if that fails. No need to catch UnicodeError:
>>> request.query['city']
'G\xc3\xb6ttingen' # A utf8 byte string
>>> request.query.city
u'Göttingen' # The same string as unicode
In Python 3 all strings are unicode, but HTTP is a byte-based wire protocol. The server has to decode the byte strings somehow before they are passed to the application. To be on the safe side, WSGI suggests ISO-8859-1 (aka latin1), a reversible single-byte codec that can be re-encoded with a different encoding later. Bottle does that for FormsDict.getunicode() and attribute access, but not for the dict-access methods. These return the unchanged values as provided by the server implementation, which is probably not what you want.
>>> request.query['city']
'Göttingen' # An utf8 string provisionally decoded as ISO-8859-1 by the server
>>> request.query.city
'Göttingen' # The same string correctly re-encoded as utf8 by bottle
If you need the whole dictionary with correctly decoded values (e.g. for WTForms), you can call FormsDict.decode() to get a re-encoded copy.
Each BaseRequest instance wraps a WSGI environment dictionary. The original is stored in BaseRequest.environ, but the request object itself behaves like a dictionary, too. Most of the interesting data is exposed through special methods or attributes, but if you want to access WSGI environ variables directly, you can do so:
@route('/my_ip')
def show_ip():
ip = request.environ.get('REMOTE_ADDR')
# or ip = request.get('REMOTE_ADDR')
# or ip = request['REMOTE_ADDR']
return "Your IP is: %s" % ip
Bottle comes with a fast and powerful built-in template engine called SimpleTemplate Engine. To render a template you can use the template() function or the view() decorator. All you have to do is to provide the name of the template and the variables you want to pass to the template as keyword arguments. Here’s a simple example of how to render a template:
@route('/hello')
@route('/hello/<name>')
def hello(name='World'):
return template('hello_template', name=name)
This will load the template file hello_template.tpl and render it with the name variable set. Bottle will look for templates in the ./views/ folder or any folder specified in the bottle.TEMPLATE_PATH list.
The view() decorator allows you to return a dictionary with the template variables instead of calling template():
@route('/hello')
@route('/hello/<name>')
@view('hello_template')
def hello(name='World'):
return dict(name=name)
Syntax
The template syntax is a very thin layer around the Python language. Its main purpose is to ensure correct indentation of blocks, so you can format your template without worrying about indentation. Follow the link for a full syntax description: SimpleTemplate Engine
Here is an example template:
%if name == 'World':
<h1>Hello {{name}}!</h1>
<p>This is a test.</p>
%else:
<h1>Hello {{name.title()}}!</h1>
<p>How are you?</p>
%end
Caching
Templates are cached in memory after compilation. Modifications made to the template files will have no affect until you clear the template cache. Call bottle.TEMPLATES.clear() to do so. Caching is disabled in debug mode.
New in version 0.9.
Bottle’s core features cover most common use-cases, but as a micro-framework it has its limits. This is where “Plugins” come into play. Plugins add missing functionality to the framework, integrate third party libraries, or just automate some repetitive work.
We have a growing List of available Plugins and most plugins are designed to be portable and re-usable across applications. The chances are high that your problem has already been solved and a ready-to-use plugin exists. If not, the Plugin Development Guide may help you.
The effects and APIs of plugins are manifold and depend on the specific plugin. The SQLitePlugin plugin for example detects callbacks that require a db keyword argument and creates a fresh database connection object every time the callback is called. This makes it very convenient to use a database:
from bottle import route, install, template
from bottle_sqlite import SQLitePlugin
install(SQLitePlugin(dbfile='/tmp/test.db'))
@route('/show/<post_id:int>')
def show(db, post_id):
c = db.execute('SELECT title, content FROM posts WHERE id = ?', (post_id,))
row = c.fetchone()
return template('show_post', title=row['title'], text=row['content'])
@route('/contact')
def contact_page():
''' This callback does not need a db connection. Because the 'db'
keyword argument is missing, the sqlite plugin ignores this callback
completely. '''
return template('contact')
Other plugin may populate the thread-safe local object, change details of the request object, filter the data returned by the callback or bypass the callback completely. An “auth” plugin for example could check for a valid session and return a login page instead of calling the original callback. What happens exactly depends on the plugin.
Plugins can be installed application-wide or just to some specific routes that need additional functionality. Most plugins can safely be installed to all routes and are smart enough to not add overhead to callbacks that do not need their functionality.
Let us take the SQLitePlugin plugin for example. It only affects route callbacks that need a database connection. Other routes are left alone. Because of this, we can install the plugin application-wide with no additional overhead.
To install a plugin, just call install() with the plugin as first argument:
from bottle_sqlite import SQLitePlugin
install(SQLitePlugin(dbfile='/tmp/test.db'))
The plugin is not applied to the route callbacks yet. This is delayed to make sure no routes are missed. You can install plugins first and add routes later, if you want to. The order of installed plugins is significant, though. If a plugin requires a database connection, you need to install the database plugin first.
Uninstall Plugins
You can use a name, class or instance to uninstall() a previously installed plugin:
sqlite_plugin = SQLitePlugin(dbfile='/tmp/test.db')
install(sqlite_plugin)
uninstall(sqlite_plugin) # uninstall a specific plugin
uninstall(SQLitePlugin) # uninstall all plugins of that type
uninstall('sqlite') # uninstall all plugins with that name
uninstall(True) # uninstall all plugins at once
Plugins can be installed and removed at any time, even at runtime while serving requests. This enables some neat tricks (installing slow debugging or profiling plugins only when needed) but should not be overused. Each time the list of plugins changes, the route cache is flushed and all plugins are re-applied.
Note
The module-level install() and uninstall() functions affect the Default Application. To manage plugins for a specific application, use the corresponding methods on the Bottle application object.
The apply parameter of the route() decorator comes in handy if you want to install plugins to only a small number of routes:
sqlite_plugin = SQLitePlugin(dbfile='/tmp/test.db')
@route('/create', apply=[sqlite_plugin])
def create(db):
db.execute('INSERT INTO ...')
You may want to explicitly disable a plugin for a number of routes. The route() decorator has a skip parameter for this purpose:
sqlite_plugin = SQLitePlugin(dbfile='/tmp/test.db')
install(sqlite_plugin)
@route('/open/<db>', skip=[sqlite_plugin])
def open_db(db):
# The 'db' keyword argument is not touched by the plugin this time.
if db in ('test', 'test2'):
# The plugin handle can be used for runtime configuration, too.
sqlite_plugin.dbfile = '/tmp/%s.db' % db
return "Database File switched to: /tmp/%s.db" % db
abort(404, "No such database.")
The skip parameter accepts a single value or a list of values. You can use a name, class or instance to identify the plugin that is to be skipped. Set skip=True to skip all plugins at once.
Most plugins are specific to the application they were installed to. Consequently, they should not affect sub-applications mounted with Bottle.mount(). Here is an example:
root = Bottle()
root.mount('/blog', apps.blog)
@root.route('/contact', template='contact')
def contact():
return {'email': 'contact@example.com'}
root.install(plugins.WTForms())
Whenever you mount an application, Bottle creates a proxy-route on the main-application that forwards all requests to the sub-application. Plugins are disabled for this kind of proxy-route by default. As a result, our (fictional) WTForms plugin affects the /contact route, but does not affect the routes of the /blog sub-application.
This behavior is intended as a sane default, but can be overridden. The following example re-activates all plugins for a specific proxy-route:
root.mount('/blog', apps.blog, skip=None)
But there is a snag: The plugin sees the whole sub-application as a single route, namely the proxy-route mentioned above. In order to affect each individual route of the sub-application, you have to install the plugin to the mounted application explicitly.
So you have learned the basics and want to write your own application? Here are some tips that might help you to be more productive.
Bottle maintains a global stack of Bottle instances and uses the top of the stack as a default for some of the module-level functions and decorators. The route() decorator, for example, is a shortcut for calling Bottle.route() on the default application:
@route('/')
def hello():
return 'Hello World'
This is very convenient for small applications and saves you some typing, but also means that, as soon as your module is imported, routes are installed to the global application. To avoid this kind of import side-effects, Bottle offers a second, more explicit way to build applications:
app = Bottle()
@app.route('/')
def hello():
return 'Hello World'
Separating the application object improves re-usability a lot, too. Other developers can safely import the app object from your module and use Bottle.mount() to merge applications together.
As an alternative, you can make use of the application stack to isolate your routes while still using the convenient shortcuts:
default_app.push()
@route('/')
def hello():
return 'Hello World'
app = default_app.pop()
Both app() and default_app() are instance of AppStack and implement a stack-like API. You can push and pop applications from and to the stack as needed. This also helps if you want to import a third party module that does not offer a separate application object:
default_app.push()
import some.module
app = default_app.pop()
During early development, the debug mode can be very helpful.
bottle.debug(True)
In this mode, Bottle is much more verbose and provides helpful debugging information whenever an error occurs. It also disables some optimisations that might get in your way and adds some checks that warn you about possible misconfiguration.
Here is an incomplete list of things that change in debug mode:
The default error page shows a traceback.
Templates are not cached.
Plugins are applied immediately.
Just make sure not to use the debug mode on a production server.
During development, you have to restart the server a lot to test your recent changes. The auto reloader can do this for you. Every time you edit a module file, the reloader restarts the server process and loads the newest version of your code.
from bottle import run
run(reloader=True)
How it works: the main process will not start a server, but spawn a new child process using the same command line arguments used to start the main process. All module-level code is executed at least twice! Be careful.
The child process will have os.environ['BOTTLE_CHILD'] set to True
and start as a normal non-reloading app server. As soon as any of the
loaded modules changes, the child process is terminated and re-spawned by
the main process. Changes in template files will not trigger a reload.
Please use debug mode to deactivate template caching.
The reloading depends on the ability to stop the child process. If you are
running on Windows or any other operating system not supporting
signal.SIGINT (which raises KeyboardInterrupt in Python),
signal.SIGTERM is used to kill the child. Note that exit handlers and
finally clauses, etc., are not executed after a SIGTERM.
Starting with version 0.10 you can use bottle as a command-line tool:
$ python -m bottle
Usage: bottle.py [options] package.module:app
Options:
-h, --help show this help message and exit
--version show version number.
-b ADDRESS, --bind=ADDRESS
bind socket to ADDRESS.
-s SERVER, --server=SERVER
use SERVER as backend.
-p PLUGIN, --plugin=PLUGIN
install additional plugin/s.
--debug start server in debug mode.
--reload auto-reload on file changes.
The ADDRESS field takes an IP address or an IP:PORT pair and defaults to localhost:8080. The other parameters should be self-explanatory.
Both plugins and applications are specified via import expressions. These consist of an import path (e.g. package.module) and an expression to be evaluated in the namespace of that module, separated by a colon. See load() for details. Here are some examples:
# Grab the 'app' object from the 'myapp.controller' module and
# start a paste server on port 80 on all interfaces.
python -m bottle -server paste -bind 0.0.0.0:80 myapp.controller:app
# Start a self-reloading development server and serve the global
# default application. The routes are defined in 'test.py'
python -m bottle --debug --reload test
# Install a custom debug plugin with some parameters
python -m bottle --debug --reload --plugin 'utils:DebugPlugin(exc=True)'' test
# Serve an application that is created with 'myapp.controller.make_app()'
# on demand.
python -m bottle 'myapp.controller:make_app()''
Bottle runs on the built-in wsgiref WSGIServer by default. This non-threading HTTP server is perfectly fine for development and early production, but may become a performance bottleneck when server load increases.
The easiest way to increase performance is to install a multi-threaded server library like paste or cherrypy and tell Bottle to use that instead of the single-threaded server:
bottle.run(server='paste')
This, and many other deployment options are described in a separate article: Deployment
Programmer code that is to be called when some external action happens. In the context of web frameworks, the mapping between URL paths and application code is often achieved by specifying a callback function for each URL.
A function returning another function, usually applied as a function transformation using the @decorator syntax. See python documentation for function definition for more about decorators.
A structure where information about all documents under the root is saved, and used for cross-referencing. The environment is pickled after the parsing stage, so that successive runs only need to read and parse new and changed documents.
A function to handle some specific event or situation. In a web framework, the application is developed by attaching a handler function as callback for each specific URL comprising the application.
The directory which, including its subdirectories, contains all source files for one Sphinx project.