Django uses request and response objects to pass state through the system.
When a page is requested, Django creates an HttpRequest object that contains metadata about the request. Then Django loads the appropriate view, passing the HttpRequest as the first argument to the view function. Each view is responsible for returning an HttpResponse object.
This document explains the APIs for HttpRequest and HttpResponse objects.
All attributes except session should be considered read-only.
A string representing the full path to the requested page, not including the domain.
Example: "/music/bands/the_beatles/"
Under some Web server configurations, the portion of the URL after the host name is split up into a script prefix portion and a path info portion (this happens, for example, when using the django.root option with the modpython handler from Apache). The path_info attribute always contains the path info portion of the path, no matter what Web server is being used. Using this instead of attr:~HttpRequest.path can make your code much easier to move between test and deployment servers.
For example, if the django.root for your application is set to "/minfo", then path might be "/minfo/music/bands/the_beatles/" and path_info would be "/music/bands/the_beatles/".
A string representing the HTTP method used in the request. This is guaranteed to be uppercase. Example:
if request.method == 'GET':
do_something()
elif request.method == 'POST':
do_something_else()
A dictionary-like object containing all given HTTP POST parameters. See the QueryDict documentation below.
It's possible that a request can come in via POST with an empty POST dictionary -- if, say, a form is requested via the POST HTTP method but does not include form data. Therefore, you shouldn't use if request.POST to check for use of the POST method; instead, use if request.method == "POST" (see above).
Note: POST does not include file-upload information. See FILES.
For convenience, a dictionary-like object that searches POST first, then GET. Inspired by PHP's $_REQUEST.
For example, if GET = {"name": "john"} and POST = {"age": '34'}, REQUEST["name"] would be "john", and REQUEST["age"] would be "34".
It's strongly suggested that you use GET and POST instead of REQUEST, because the former are more explicit.
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 an UploadedFile as described below.
See Managing files for more information.
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". Otherwise, FILES will be a blank dictionary-like object.
A standard Python dictionary containing all available HTTP headers. Available headers depend on the client and server, but here are some examples:
- CONTENT_LENGTH
- CONTENT_TYPE
- HTTP_ACCEPT_ENCODING
- HTTP_ACCEPT_LANGUAGE
- HTTP_HOST -- The HTTP Host header sent by the client.
- HTTP_REFERER -- The referring page, if any.
- HTTP_USER_AGENT -- The client's user-agent string.
- QUERY_STRING -- The query string, as a single (unparsed) string.
- REMOTE_ADDR -- The IP address of the client.
- REMOTE_HOST -- The hostname of the client.
- REMOTE_USER -- The user authenticated by the Web server, if any.
- REQUEST_METHOD -- A string such as "GET" or "POST".
- SERVER_NAME -- The hostname of the server.
- SERVER_PORT -- The port of the server.
With the exception of CONTENT_LENGTH and CONTENT_TYPE, as given above, any HTTP headers in the request are converted to META keys by converting all characters to uppercase, replacing any hyphens with underscores and adding an HTTP_ prefix to the name. So, for example, a header called X-Bender would be mapped to the META key HTTP_X_BENDER.
A django.contrib.auth.models.User object representing the currently logged-in user. If the user isn't currently logged in, user will be set to an instance of django.contrib.auth.models.AnonymousUser. You can tell them apart with is_authenticated(), like so:
if request.user.is_authenticated():
# Do something for logged-in users.
else:
# Do something for anonymous users.
user is only available if your Django installation has the AuthenticationMiddleware activated. For more, see User authentication in Django.
The raw HTTP POST data as a byte string. This is useful for processing data in different formats than of conventional HTML forms: binary images, XML payload etc. For processing form data use HttpRequest.POST.
You can also read from an HttpRequest using file-like interface. See HttpRequest.read().
Returns the originating host of the request using information from the HTTP_X_FORWARDED_HOST and HTTP_HOST headers (in that order). If they don't provide a value, the method uses a combination of SERVER_NAME and SERVER_PORT as detailed in PEP 333.
Example: "127.0.0.1:8000"
Note
The get_host() method fails when the host is behind multiple proxies. One solution is to use middleware to rewrite the proxy headers, as in the following example:
class MultipleProxyMiddleware(object):
FORWARDED_FOR_FIELDS = [
'HTTP_X_FORWARDED_FOR',
'HTTP_X_FORWARDED_HOST',
'HTTP_X_FORWARDED_SERVER',
]
def process_request(self, request):
"""
Rewrites the proxy headers so that only the most
recent proxy is used.
"""
for field in self.FORWARDED_FOR_FIELDS:
if field in request.META:
if ',' in request.META[field]:
parts = request.META[field].split(',')
request.META[field] = parts[-1].strip()
Returns the path, plus an appended query string, if applicable.
Example: "/music/bands/the_beatles/?print=true"
Returns the absolute URI form of location. If no location is provided, the location will be set to request.get_full_path().
If the location is already an absolute URI, it will not be altered. Otherwise the absolute URI is built using the server variables available in this request.
Example: "http://example.com/music/bands/the_beatles/?print=true"
Methods implementing a file-like interface for reading from an HttpRequest instance. This makes it possible to consume an incoming request in a streaming fashion. A common use-case would be to process a big XML payload with iterative parser without constructing a whole XML tree in memory.
Given this standard interface, an HttpRequest instance can be passed directly to an XML parser such as ElementTree:
import xml.etree.ElementTree as ET
for element in ET.iterparse(request):
process(element)
In an HttpRequest object, the GET and POST attributes are instances of django.http.QueryDict. QueryDict is a dictionary-like class customized to deal with multiple values for the same key. This is necessary because some HTML form elements, notably <select multiple="multiple">, pass multiple values for the same key.
QueryDict instances are immutable, unless you create a copy() of them. That means you can't change attributes of request.POST and request.GET directly.
QueryDict implements all the standard dictionary methods, because it's a subclass of dictionary. Exceptions are outlined here:
Takes either a QueryDict or standard dictionary. Just like the standard dictionary update() method, except it appends to the current dictionary items rather than replacing them. For example:
>>> q = QueryDict('a=1')
>>> q = q.copy() # to make it mutable
>>> q.update({'a': '2'})
>>> q.getlist('a')
[u'1', u'2']
>>> q['a'] # returns the last
[u'2']
Just like the standard dictionary items() method, except this uses the same last-value logic as __getitem__(). For example:
>>> q = QueryDict('a=1&a=2&a=3')
>>> q.items()
[(u'a', u'3')]
Just like the standard dictionary values() method, except this uses the same last-value logic as __getitem__(). For example:
>>> q = QueryDict('a=1&a=2&a=3')
>>> q.values()
[u'3']
In addition, QueryDict has the following methods:
Like items(), except it includes all values, as a list, for each member of the dictionary. For example:
>>> q = QueryDict('a=1&a=2&a=3')
>>> q.lists()
[(u'a', [u'1', u'2', u'3'])]
Returns a string of the data in query-string format. Example:
>>> q = QueryDict('a=2&b=3&b=5')
>>> q.urlencode()
'a=2&b=3&b=5'
Optionally, urlencode can be passed characters which do not require encoding. For example:
>>> q = QueryDict('', mutable=True)
>>> q['next'] = '/a&b/'
>>> q.urlencode(safe='/')
'next=/a%26b/'
In contrast to HttpRequest objects, which are created automatically by Django, HttpResponse objects are your responsibility. Each view you write is responsible for instantiating, populating and returning an HttpResponse.
The HttpResponse class lives in the django.http module.
Typical usage is to pass the contents of the page, as a string, to the HttpResponse constructor:
>>> response = HttpResponse("Here's the text of the Web page.")
>>> response = HttpResponse("Text only, please.", mimetype="text/plain")
But if you want to add content incrementally, you can use response as a file-like object:
>>> response = HttpResponse()
>>> response.write("<p>Here's the text of the Web page.</p>")
>>> response.write("<p>Here's another paragraph.</p>")
Finally, you can pass HttpResponse an iterator rather than passing it hard-coded strings. If you use this technique, follow these guidelines:
- The iterator should return strings.
- If an HttpResponse has been initialized with an iterator as its content, you can't use the class:HttpResponse instance as a file-like object. Doing so will raise Exception.
To set or remove a header in your response, treat it like a dictionary:
>>> response = HttpResponse()
>>> response['Cache-Control'] = 'no-cache'
>>> del response['Cache-Control']
Note that unlike a dictionary, del doesn't raise KeyError if the header doesn't exist.
HTTP headers cannot contain newlines. An attempt to set a header containing a newline character (CR or LF) will raise BadHeaderError
To tell the browser to treat the response as a file attachment, use the mimetype argument and set the Content-Disposition header. For example, this is how you might return a Microsoft Excel spreadsheet:
>>> response = HttpResponse(my_data, mimetype='application/vnd.ms-excel')
>>> response['Content-Disposition'] = 'attachment; filename=foo.xls'
There's nothing Django-specific about the Content-Disposition header, but it's easy to forget the syntax, so we've included it here.
Instantiates an HttpResponse object with the given page content (a string) and MIME type. The :setting:`DEFAULT_CONTENT_TYPE` is 'text/html'.
content can be an iterator or a string. If it's an iterator, it should return strings, and those strings will be joined together to form the content of the response.
status is the HTTP Status code for the response.
content_type is an alias for mimetype. Historically, this parameter was only called mimetype, but since this is actually the value included in the HTTP Content-Type header, it can also include the character set encoding, which makes it more than just a MIME type specification. If mimetype is specified (not None), that value is used. Otherwise, content_type is used. If neither is given, the :setting:`DEFAULT_CONTENT_TYPE` setting is used.
The possibility of specifying a datetime.datetime object in expires, and the auto-calculation of max_age in such case was added. The httponly argument was also added.
Sets a cookie. The parameters are the same as in the cookie Morsel object in the Python standard library.
max_age should be a number of seconds, or None (default) if the cookie should last only as long as the client's browser session. If expires is not specified, it will be calculated.
expires should either be a string in the format "Wdy, DD-Mon-YY HH:MM:SS GMT" or a datetime.datetime object in UTC. If expires is a datetime object, the max_age will be calculated.
Use domain if you want to set a cross-domain cookie. For example, domain=".lawrence.com" will set a cookie that is readable by the domains www.lawrence.com, blogs.lawrence.com and calendars.lawrence.com. Otherwise, a cookie will only be readable by the domain that set it.
Use httponly=True if you want to prevent client-side JavaScript from having access to the cookie.
HTTPOnly is a flag included in a Set-Cookie HTTP response header. It is not part of the RFC2109 standard for cookies, and it isn't honored consistently by all browsers. However, when it is honored, it can be a useful way to mitigate the risk of client side script accessing the protected cookie data.
Deletes the cookie with the given key. Fails silently if the key doesn't exist.
Due to the way cookies work, path and domain should be the same values you used in set_cookie() -- otherwise the cookie may not be deleted.
Django includes a number of HttpResponse subclasses that handle different types of HTTP responses. Like HttpResponse, these subclasses live in django.http.
Mar 31, 2011