The Swiss Army Knife For Python Web Developers
The wrappers are simple request and response objects which you can subclass to do whatever you want them to do. The request object contains the information transmitted by the client (webbrowser) and the response object contains all the information sent back to the browser.
An important detail is that the request object is created with the WSGI environ and will act as high-level proxy whereas the response object is an actual WSGI application.
Like everything else in Werkzeug these objects will work correctly with unicode data. Incoming form data parsed by the response object will be decoded into an unicode object if possible and if it makes sense.
You can import all these objects directly from werkzeug.
These objects implement a common set of operations. They are missing fancy addon functionality like user agent parsing or etag handling. These features are available by mixing in various mixin classes or using Request and Response.
Very basic request object. This does not implement advanced stuff like entity tag parsing or cache controls. The request object is created with the WSGI environment as first argument and will add itself to the WSGI environment as 'werkzeug.request' unless it’s created with populate_request set to False.
There are a couple of mixins available that add additional functionality to the request object, there is also a class called Request which subclasses BaseRequest and all the important mixins.
It’s a good idea to create a custom subclass of the BaseRequest and add missing functionality either via mixins or direct implementation. Here an example for such subclasses:
from werkzeug import BaseRequest, ETagRequestMixin class Request(BaseRequest, ETagRequestMixin): pass
Request objects should be considered read only. Even though the object doesn’t enforce read only access everywhere you should never modify any data on the object itself unless you know exactly what you are doing.
Per default the request object will assume all the text data is utf-8 encoded. Please refer to the unicode chapter for more details about customizing the behavior.
Creating Request Objects
Per default the request object will be added to the WSGI enviornment as werkzeug.request to support the debugging system. If you don’t want that, set populate_request to False.
If shallow is True the environment is initialized as shallow object around the environ. Every operation that would modify the environ in any way (such as consuming form data) raises an exception unless the shallow attribute is explicitly set to False. This is useful for middlewares where you don’t want to consume the form data by accident. A shallow request is not populated to the WSGI environment.
Create a new request object based on the values provided. If environ is given missing values are filled from there. This method is useful for small scripts when you need to simulate a request from an URL. Do not use this method for unittesting, there is a full featured client object in werkzeug.test that allows to create multipart requests etc.
This accepts the same options as the create_environ function from the utils module and additionally an environ parameter that can contain values which will override the values from dict returned by create_environ.
Additionally a dict passed to query_string will be encoded in the request class charset.
returns: request object
Decorate a function as responder that accepts the request as first argument. This works like the responder decorator but the function is passed the request object as first argument:
@Request.application def my_wsgi_app(request): return Response('Hello World!')
Properties
A dictionary-like object containing all given HTTP POST parameters. See the MultiDict documentation in the utils section.
This dict does not contain uploaded files, see files regarding that.
A dictionary-like object containing all uploaded files. Each key in files is the name from the <input type="file" name="" />. Each value in files is a Werkzeug FileStorage object with the following members:
Note that files will only contain data if the request method was POST and the <form> that posted to the request had enctype="multipart/form-data". It will be empty otherwise.
See the MultiDict / FileStorage documentation in the utils section for more details about the used data structure.
Base response class. The most important fact about a response object is that it’s a regular WSGI application. It’s initialized with a couple of response parameters (headers, body, status code etc.) and will start a valid WSGI response when called with the environ and start response callable.
Because it’s a WSGI application itself processing usually ends before the actual response is sent to the server. This helps debugging systems because they can catch all the exceptions before responses are started.
Here a small example WSGI application that takes advantage of the response objects:
from werkzeug import BaseResponse as Response def index(): return Response('Index page') def application(environ, start_response): path = environ.get('PATH_INFO') or '/' if path == '/': response = index() else: response = Response('Not Found', status=404) return response(environ, start_response)
Like BaseRequest which object is lacking a lot of functionality implemented in mixins. This gives you a better control about the actual API of your response objects, so you can create subclasses and add custom functionality. A full featured response object is available as Response which implements a couple of useful mixins.
To enforce a new type of already existing responses you can use the force_type method. This is useful if you’re working with different subclasses of response objects and you want to post process them with a know interface.
Per default the request object will assume all the text data is utf-8 encoded. Please refer to the unicode chapter for more details about customizing the behavior.
Creating Response Objects
Response can be any kind of iterable or string. If it’s a string it’s considered being an iterable with one item which is the string passed. Headers can be a list of tuples or a Headers object.
Special note for mimetype and content_type. For most mime types mimetype and content_type work the same, the difference affects only ‘text’ mimetypes. If the mimetype passed with mimetype is a mimetype starting with text/ it becomes a charset parameter defined with the charset of the response object. In constrast the content_type parameter is always added as header unmodified.
Enforce that the WSGI response is a response object of the current type. Werkzeug will use the BaseResponse internally in many situations like the exceptions. If you call get_response on an exception you will get back a regular BaseResponse object, even if you are using a custom subclass.
This method can enforce a given response type, and it will also convert arbitrary WSGI callables into response objects if an environ is provided:
# convert a Werkzeug response object into an instance of the # MyResponseClass subclass. response = MyResponseClass.force_type(response) # convert any WSGI application into a response object response = MyResponseClass.force_type(response, environ)
This is especially useful if you want to post-process responses in the main dispatcher and use functionality provided by your subclass.
Keep in mind that this will modify response objects in place if possible!
Properties
If the response is streamed (the response is not a sequence) this property is True. In this case streamed means that there is no information about the number of iterations. This is usully True if a generator is passed to the response object.
This is useful for checking before applying some sort of post filtering that should not take place for streamed responses.
Methods
Sets a cookie. The parameters are the same as in the cookie Morsel object in the Python standard library but it accepts unicode data too:
cookie should last only as long as the client’s browser session.
expires should be a datetime object or UNIX timestamp.
Use domain if you want to set a cross-domain cookie. For example, domain=".example.com" will set a cookie that is readable by the domain www.example.com, foo.example.com etc. Otherwise, a cookie will only be readable by the domain that set it.
path limits the cookie to a given path, per default it will span the whole domain.
Werkzeug also provides helper mixins for various HTTP related functionality such as etags, cache control, user agents etc. When subclassing you can mix those classes in to extend the functionality of the BaseRequest or BaseResponse object. Here a small example for a request object that parses accept headers:
from werkzeug import BaseRequest, AcceptMixin class Request(BaseRequest, AcceptMixin): pass
The Request and Response classes subclass the BaseRequest and BaseResponse classes and implement all the mixins Werkzeug provides:
Full featured request object implementing the following mixins:
Full featured response object implementing the following mixins:
A mixin for classes with an environ attribute to get and all the HTTP accept headers as Accept objects. This can be mixed in request objects or any other object that has a WSGI environ available as environ.
All this properties store Accept objects as documented in the utils section.
Adds an authorization property that represents the parsed value of the Authorization header as Authorization object.
Add entity tag and cache descriptors to a request object or object with an WSGI environment available as environ. This not only provides access to etags but also to the cache control header.
All the used data structures are documented in the utils section.
Adds extra functionality to a response object for etag and cache handling. This mixin requires an object with at least a headers object that implements a dict like interface similar to Headers.
Make the response conditional to the request. This method works best if an etag was defined for the response already. The add_etag method can be used to do that. If called without etag just the date header is set.
This does nothing if the request method in the request or enviorn is anything but GET or HEAD.
It does not remove the body of the response because that’s something the __call__ function does for us automatically.
Returns self so that you can do return resp.make_conditional(req) but modifies the object in-place.
Mixin for BaseRequest subclasses. Classes that inherit from this mixin will automatically get a stream property that provides a write-only interface to the response iterable.
A mixin for BaseResponse subclasses. Response objects that mix this class in will automatically get descriptors for a couple of HTTP headers with automatic type conversion.
The Age response-header field conveys the sender’s estimate of the amount of time since the response (or its revalidation) was generated at the origin server.
Age values are non-negative decimal integers, representing time in seconds.
The Retry-After response-header field can be used with a 503 (Service Unavailable) response to indicate how long the service is expected to be unavailable to the requesting client.
Time in seconds until expiration or date.
Adds a www_authenticate property to a response object.
Adds a user_agent attribute to the request object which contains the parsed user agent of the browser that triggered the request as UserAgent object.
File uploads are a tricky thing in general. Per default all the file uploads go into temporary files on the filesystem and not the memory of the current process to avoid high memory usage. You could also change that to store the data somewhere else by implementing an object that implements the python IO protocol (see StringIO) for both writing and reading.
Then you have to subclass a request object and override _get_file_stream:
Called to get a stream for the file upload.
This must provide a file-like class with read(), readline() and seek() methods that is both writeable and readable.
The default implementation returns a temporary file.