Routing system

As introduced in the Getting Started chapter, the weppy routing system doesn't use a table or a separated file logic, but it's explicit indeed, using the route decorator on your functions.

Exposing functions

The route method of the App object accepts several parameters, as you can see from the source code:

def route(self, path=None, name=None, template=None, handlers=None,
           helpers=None, schemes=None, hostname=None, methods=None,
           prefix=None, template_folder=None, template_path=None):

Let's see them in detail.


The path parameter is the first and the most important parameter you can pass to route, in fact it tells weppy on which url should the function been exposed; still, you seen from the code that is None by default. What does it mean? Simply, when you don't pass the path parameter to route, it will route your function on the url with the same name of your function. So if you write:

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:

def user(username):
    return "Hello %s" % username

def double(number):
    return "%d * 2 = %d" % (number, number*2)

It's quite simple, isn't it? And here is the complete list of types of variables you can use:

type specification
int accepts integers
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 weppy will return a 404 error.

Sometimes you also need your variable rules to be conditional, and accepts requests on the same function with, for example, /profile/123432 and /profile. weppy allows you to do that using the conditional regex notation:

def profile(user_id):
    if user_id:
        # get requested user
        # load current logged user profile

and as you thought, when conditional arguments are not given in the requested url, your function's parameters will be None.

Now, it's time to see the methods parameter of route()


The template parameter allows you to set a specific template for the function you're exposing.
By default weppy search for a template with the same name of the function, so with an example:

def profile():
    # code

will search for the profile.html template in your application's template folder. When you need to use a different template name, just tell weppy to load it:



HTTP knows different methods for accessing URLs. By default, a weppy route only answers to GET and POST requests, but that can be changed easily:

@app.route("/onlyget", methods="get")
def f():
    # code

@app.route("/post", methods=["post", "delete"])
def g():
    # code

Other parameters

If you read the Getting started chapter, you should know that weppy provides the Handler class to perform operations during requests. The handlers and helpers parameters of route() allows you to bind them on the exposed function.

Similarly to the methods parameter, the schemes one allows you to tell weppy on which HTTP schemes the function should answer (by default both http and https methods are allowed); while if you need to bind the exposed function to a specific host, you can use the hostname parameter.

The prefix, template_path and template_folder parameters are specific to AppModules and there's no a specific need to use them directly in the app.route() function.

The url() function

weppy provides a useful method to create urls for your exposed functions, let's see how it works:

from weppy import App, url
app = App(__name__)

def index():
    # code

def g():

def f(a, b):
    # code

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: * / * /anotherurl?u=2 * /find/foo/bar * /post/123/edit

Basically, you just need to call url() with the name of your function, and eventually the arguments needed by the function.

URLs with application modules

As we seen in the Application modules chapter, above, the name parameter of AppModule object is used by weppy for the namespacing of the urls. What does it mean?
When you call the weppy url() helper, you send as first parameter the name of the function you have exposed. But if you have and 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

Static files

Quite often you will need to link static contents (images, CSS, JavaScripts) into your application. You would create a folder called static in your package or next to your module and 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

Calling url() for static files is useful instead of manually write the url for the file because you can enable the static versioning in your weppy application.

When an application is in development, static files can change often, but when your application goes to production you may want to serve static files with cache headers to prevent un-necessary downloads, saving bandwidth and load, since static files do not change often. But when they do, browsers should load the new ones and not the old cached.
weppy solves the problem for you, allowing you to configure your application with a static_version:

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. And when you release a new version of your application with changed static files, you just need to change the static_version string.