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# API Levels

Werkzeug is intended to be a utility rather than a framework. Because of that the user-friendly API is separated from the lower-level API so that Werkzeug can easily be used to extend another system.

All the functionality the `Request` and `Response` objects (aka the “wrappers”) provide is also available in small utility functions.

## Example

This example implements a small Hello World application that greets the user with the name entered:

    from werkzeug.utils import escape
    from werkzeug.wrappers import Request, Response

    @Request.application
    def hello_world(request):
        result = ['<title>Greeter</title>']
        if request.method == 'POST':
            result.append('<h1>Hello %s!</h1>' % escape(request.form['name']))
        result.append('''
            <form action="" method="post">
                <p>Name: <input type="text" name="name" size="20">
                <input type="submit" value="Greet me">
            </form>
        ''')
        return Response(''.join(result), mimetype='text/html')

Alternatively the same application could be use without request and response objects but by taking advantage of the parsing functions werkzeug provides:

    from werkzeug.formparser import parse_form_data
    from werkzeug.utils import escape

    def hello_world(environ, start_response):
        result = ['<title>Greeter</title>']
        if environ['REQUEST_METHOD'] == 'POST':
            form = parse_form_data(environ)[1]
            result.append('<h1>Hello %s!</h1>' % escape(form['name']))
        result.append('''
            <form action="" method="post">
                <p>Name: <input type="text" name="name" size="20">
                <input type="submit" value="Greet me">
            </form>
        ''')
        start_response('200 OK', [('Content-Type', 'text/html; charset=utf-8')])
        return [''.join(result)]

## High or Low?

Usually you want to use the high-level layer (the request and response objects). But there are situations where this might not be what you want.

For example you might be maintaining code for an application written in Django or another framework and you have to parse HTTP headers. You can utilize Werkzeug for that by accessing the lower-level HTTP header parsing functions.

Another situation where the low level parsing functions can be useful are custom WSGI frameworks, unit-testing or modernizing an old CGI/mod_python application to WSGI as well as WSGI middlewares where you want to keep the overhead low.