Recipes

This is a collection of code snippets and examples for common use cases.

Keeping track of Sessions

There is no built-in support for sessions because there is no right way to do it (in a micro framework). Depending on requirements and environment you could use beaker middleware with a fitting backend or implement it yourself. Here is an example for beaker sessions with a file-based backend:

import bottle
from beaker.middleware import SessionMiddleware

session_opts = {
    'session.type': 'file',
    'session.cookie_expires': 300,
    'session.data_dir': './data',
    'session.auto': True
}
app = SessionMiddleware(bottle.app(), session_opts)

@bottle.route('/test')
def test():
  s = bottle.request.environ.get('beaker.session')
  s['test'] = s.get('test',0) + 1
  s.save()
  return 'Test counter: %d' % s['test']

bottle.run(app=app)

Debugging with Style: Debugging Middleware

Bottle catches all Exceptions raised in your app code to prevent your WSGI server from crashing. If the built-in debug() mode is not enough and you need exceptions to propagate to a debugging middleware, you can turn off this behaviour:

import bottle
app = bottle.app()
app.catchall = False #Now most exceptions are re-raised within bottle.
myapp = DebuggingMiddleware(app) #Replace this with a middleware of your choice (see below)
bottle.run(app=myapp)

Now, bottle only catches its own exceptions (HTTPError, HTTPResponse and BottleException) and your middleware can handle the rest.

The werkzeug and paste libraries both ship with very powerfull debugging WSGI middleware. Look at werkzeug.debug.DebuggedApplication for werkzeug and paste.evalexception.middleware.EvalException for paste. They both allow you do inspect the stack and even execute python code within the stack context, so do not use them in production.

Embedding other WSGI Apps

This is not the recommend way (you should use a middleware in front of bottle to do this) but you can call other WSGI applications from within your bottle app and let bottle act as a pseudo-middleware. Here is an example:

from bottle import request, response, route
subproject = SomeWSGIApplication()

@route('/subproject/:subpath#.*#', method='ALL')
def call_wsgi(subpath):
    new_environ = request.environ.copy()
    new_environ['SCRIPT_NAME'] = new_environ.get('SCRIPT_NAME','') + '/subproject'
    new_environ['PATH_INFO'] = '/' + subpath
    def start_response(status, headerlist):
        response.status = int(status.split()[0])
        for key, value in headerlist:
            response.add_header(key, value)
    return app(new_environ, start_response)

Again, this is not the recommend way to implement subprojects. It is only here because many people asked for this and to show how bottle maps to WSGI.

Ignore trailing slashes

For Bottle, /example and /example/ are two different routes. To treat both URLs the same you can add two @route decorators:

@route('/test')
@route('/test/')
def test(): return 'Slash? no?'

or add a WSGI middleware that strips trailing slashes from all URLs:

class StripPathMiddleware(object):
  def __init__(self, app):
    self.app = app
  def __call__(self, e, h):
    e['PATH_INFO'] = e['PATH_INFO'].rstrip('/')
    return self.app(e,h)

app = bottle.app()
myapp = StripPathMiddleware(app)
bottle.run(app=appmy)