Tremolo uses only basic routing and built-in re module. There are no difficult abstractions, and never will.

Basic

The following will handle http://example.com/hello and query string (if any).

@app.route('/hello')
async def hello_world(**server):
    yield b'Hello '
    yield b'world!'

Regular expression

To be recognized as a regex string, at least the path must start with ^ or end with $ character.

The following will match for example with http://example.com/page/12, http://example.com/page/101, and so on.

@app.route(r'^/page/(?P<page_id>\d+)')
async def my_page(request):
    page_id = request.params.path.get('page_id', b'1')

    # Tremolo often uses bytes-like objects as is,
    # rather than converting to str or int.
    # so do not assume page_id is an int.
    yield b'You are on page ' + page_id

The regex syntax above uses named groups which you can learn more about at https://docs.python.org/3/library/re.html#re.Match.groupdict

You can always check what kind of data is received if using regex in request.params.path. It’s a dict object.

Alternatively, the matching results will be populated in kwargs as long as the names don’t conflict with server objects. So this style works too:

@app.route(r'^/page/(?P<page_id>\d+)')
async def my_page(request, page_id=b'1', **server):
    yield b'You are on page ' + page_id

regex-based routing pattern will be compared against request.url not request.path, meaning the match involves also query string.

Custom 404 page

@app.error(404)
async def my_error_page(**server):
    return 'This is my custom 404 page.'