Routing system

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

Exposing functions

Changed in 1.0

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, pipeline=None, injectors=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 which URL should the function been exposed on; still, you've seen from the code that path is None by default. What does this 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? 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 weppy 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 and Pendulum.

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

def profile(user_id):
    if user_id:
        # get requested user
        # 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.

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


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. Use a list if you want to accept more than one kind of list:

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

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


The template parameter allows you to set a specific template for the function you're exposing. By default, weppy searches for a template with the same name as the function:

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 weppy to load it:


Other parameters

weppy 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 weppy 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.

The prefix, template_path, and template_folder parameters are specific to application modules, and there's no 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 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

URLs with application modules

As we seen in the Application modules chapter, above, the name parameter of the AppModule object is used by weppy for the namespacing of the URLs. What does this mean? When you call the weppy 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

Static files

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

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 weppy 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. weppy 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.

Multiple paths

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'])
def comments(pid=None):
    if pid:
        # code to fetch the post comments
        # code to fetch all the comments

Note: mind that both the paths will have the same routing pipeline.

Under the default behavior, weppy 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')
>>> url('comments.1', 12)