As introduced in the Getting Started chapter, the Emmett routing system doesn't use a table or separated file logic, but it's explicit indeed, using the route
decorator on your functions.
Changed in version 2.0
The route
method of the App
object accepts several parameters, as you can see from this table:
parameter | type | default | description |
---|---|---|---|
paths | Union[str, List[str]] |
function name | paths on which route the function |
name | str |
function name | name for internal routing |
template | str |
function name | name of the template file |
pipeline | List[Pipe] |
route specific pipeline | |
injectors | List[Injector] |
route specific injectors | |
schemes | Union[str, List[str]] |
http, https | protocol schemes |
hostname | str |
hostname on which route the function | |
methods | List[str] |
get, post, head | HTTP methods for the route |
output | str |
auto | type of output to expect from the route |
Let's see them in detail.
The paths
parameter is the first and the most important parameter you can pass to route
. In fact, it tells Emmett which URL should the function been exposed on; still, you've seen from the upper table that paths
has an implicit value by default.
What does this mean? Simply, when you don't pass the paths
parameter to route, it will route your function on the URL with the same name of your function. So if you write:
@app.route()
async def user():
# code
your user()
function will be routed on /user.
To add variable parts to a path, you can mark these special sections as <type:variable_name>
and the variables will be passed as a keyword argument to your functions. Let's see some examples:
@app.route('/user/<str:username>')
async def user(username):
return "Hello %s" % username
@app.route('/double/<int:number>')
async def double(number):
return "%d * 2 = %d" % (number, number*2)
It's quite simple, isn't it? Here is the complete list of types of variables you can use:
type | specification |
---|---|
int | accepts integers |
float | accepts floats in dot notation |
str | accepts strings |
date | accepts date strings in format YYYY-MM-DD |
alpha | accepts strings containing only literals |
any | accepts any path (also with slashes) |
So, basically, if we try to open the URL for the double
function of the last example with a string, like /double/foo, it won't match and Emmett will return a 404 error.
Note: the int, float and date variables are casted to the relevant objects, so the parameters passed to your function will be of tipe
int
,float
andpendulum.Datetime
.
Sometimes you also need your variable rules to be conditional, and accept requests on the same function with, for example, /profile/123432 and /profile. Emmett allows you to do that using conditional regex notation:
@app.route("/profile(/<int:user_id>)?")
async def profile(user_id):
if user_id:
# get requested user
else:
# load current logged user profile
As you thought, when conditional arguments are not given in the requested URL, your function's parameters will be None
.
HTTP knows different methods for accessing URLs. By default, an Emmett route only answers to GET, POST and HEAD requests, but that can be changed easily. Use a list if you want to accept more than one kind:
@app.route("/onlyget", methods="get")
async def f():
# code
@app.route("/post", methods=["post", "delete"])
async def g():
# code
The template
parameter allows you to set a specific template for the function you're exposing. By default, Emmett searches for a template with the same name as the function:
@app.route()
async def profile():
# code
will search for the profile.html template in your application's templates folder. When you need to use a different template name, just tell Emmett to load it:
@app.route(template="mytemplate.html")
New in version 2.0
The output
parameter can be used to increase Emmett's performance in building the proper response from the exposed function. Here is the list of accepted outputs:
output | description |
---|---|
auto | automatically detects the return type |
bytes | bytes string return value |
str | str return value |
template | dict return value to be used in templates |
Under normal circumstances, the default behaviour is the best for most of usage cases.
Note:
Pipe
objects can set output too. Emmett's service pipes already implement the correct output for your routes.
Warning: returning incorrect values for the selected output type can led to unexpected errors.
Emmett provides the Pipe class to perform operations during requests. The pipeline
and injectors
parameters of route()
allows you to bind them on the exposed function.
Similar to the methods
parameter, schemes
allows you to tell Emmett on which HTTP schemes the function should answer. By default, both HTTP and HTTPS methods are allowed. If you need to bind the exposed function to a specific host, you can use the hostname
parameter.
New in version 2.0
As we saw for the route
method, the websocket
one accepts similar parameters too, as you can see from this table:
parameter | type | default | description |
---|---|---|---|
paths | Union[str, List[str]] |
function name | paths on which route the socket |
name | str |
function name | name for internal routing |
pipeline | List[Pipe] |
websocket specific pipeline | |
schemes | Union[str, List[str]] |
ws, wss | protocol schemes |
hostname | str |
hostname on which route the socket |
All the parameters works in the same way of the route
method.
Emmett provides a useful method to create URLs for your exposed functions. Let's see how it works:
from emmett import App, url
app = App(__name__)
@app.route("/")
async def index():
# code
@app.route("/anotherurl")
def g():
#code
@app.route("/find/<str:a>/<str:b>")
def f(a, b):
# code
@app.route("/post/<int:id>/edit")
def edit(id):
# code
a = url('index')
b = url('g', params={'u': 2})
c = url('f', ['foo', 'bar'])
d = url('edit', 123)
The above URLs a
, b
, c
and d
will be respectively converted to:
Basically, you just need to call url()
with the name of your function, and the arguments needed by the function.
Here is the complete list of url
accepted parameters:
parameter | description |
---|---|
path | name of the route or absolute path |
args | list of route variables (single string argument accepted) |
params | dictionary of query parameters |
anchor | anchor(s) for the url |
sign | a callable method that should produce a signature for the url |
scheme | scheme for the url (can be http or https) |
host | host for the url |
language | specify a language of the application to localize the url |
Since the websockets router is separated from the standard one, whenever you need to build an URL for websockets, you can use the url.ws()
helper.
The behaviour is exactly the same of the standard url()
helper with the exception it doesn't accept the anchor
and sign
arguments, and the value of the scheme
argument should be ws or wss.
As we seen in the Application modules chapter, above, the name
parameter of the AppModule
object is used by Emmett for the namespacing of the URLs. What does this mean? When you call the Emmett url()
helper, you send the name of the function you have exposed as the first parameter. However, if you have an index
function in your main application file, and another index
function in your module, what will you pass to the url()
?
This is why AppModule
requires the name
parameter, as it will be used for the module functions' URLs.
In fact, when you have modules in your application there are two additional notations for the url()
function:
call | end point |
---|---|
url('index') |
index function in the main application file |
url('blog.index') |
index function in the module with name="blog" |
url('.index') |
index function of the same module where you call url() |
We need to clarify that the third notation can be used only during the request flow, which translates into this statement:
You can use
url()
dot notation only inside exposed methods (or methods invoked by these) and templates
Changed in version 2.2
Quite often, you will need to link static contents (images, CSS, JavaScript) into your application. After creating a folder called static in your package or next to your module, it will be available at /static on the application.
To generate URLs for static files, use the special static
first argument:
url('static', 'js/common.js')
that will point to the file in static/js/common.js.
In case you defined custom static folders or paths inside your application modules, you can generate the appropriate URLs using the appropriate notations, for example:
url('module.static', 'js/common.js')
url('.static', 'js/common.js')
with the latter available within the module itself.
Calling url()
for static files instead of manually write the URL for the file is useful because you can enable the static versioning in your Emmett application.
When an application is in development, static files can change often, but when your application goes to production static files tend to be stable. You may want to serve static files with cache headers to prevent un-necessary downloads, saving bandwidth and load. However, browsers should load the latest versions and not the old cached ones. Emmett solves the problem for you, allowing you to configure your application with a static_version
:
app.config.static_version_urls = True
app.config.static_version = "1.0.0"
then a call to url('static', 'myfile.js')
will produce the URL /static/_1.0.0/myfile.js automatically. When you release a new version of your application with changed static files, you just need to update the static_version
string.
New in version 1.0
Sometimes you might need to route several paths to the same exposed method. Whenever you need this, you can specify a list of paths for the involved route.
Let's say, for example, you need to route a method that expose the comments of your blog, and you want to use the same method both in case the client needs all the comments, or just the ones referred to a specific post. Then you can write:
@app.route(['/comments', '/post/<int:pid>/comments'])
async def comments(pid=None):
if pid:
# code to fetch the post comments
else:
# code to fetch all the comments
Note: mind that both the paths will have the same routing pipeline.
Under the default behavior, Emmett will use the first path for building urls, while the other ones are accessible with a dot notation and the array position. For instance, for the example route we just defined above, you can build these urls:
>>> url('comments')
/comments
>>> url('comments.1', 12)
/post/12/comments