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20.22. http.cookiejar — Cookie handling for HTTP clients
Source code: Lib/http/cookiejar.py
The http.cookiejar module defines classes for automatic handling of HTTP cookies. It is useful for accessing web sites that require small pieces of data – cookies – to be set on the client machine by an HTTP response from a web server, and then returned to the server in later HTTP requests.
Both the regular Netscape cookie protocol and the protocol defined by RFC 2965 are handled. RFC 2965 handling is switched off by default. RFC 2109 cookies are parsed as Netscape cookies and subsequently treated either as Netscape or RFC 2965 cookies according to the ‘policy’ in effect. Note that the great majority of cookies on the Internet are Netscape cookies. http.cookiejar attempts to follow the de-facto Netscape cookie protocol (which differs substantially from that set out in the original Netscape specification), including taking note of the max-age and port cookie-attributes introduced with RFC 2965.
Note
The various named parameters found in Set-Cookie and Set-Cookie2 headers (eg. domain and expires) are conventionally referred to as attributes. To distinguish them from Python attributes, the documentation for this module uses the term cookie-attribute instead.
The module defines the following exception:
Instances of FileCookieJar raise this exception on failure to load cookies from a file. LoadError is a subclass of IOError.
The following classes are provided:
policy is an object implementing the CookiePolicy interface.
The CookieJar class stores HTTP cookies. It extracts cookies from HTTP requests, and returns them in HTTP responses. CookieJar instances automatically expire contained cookies when necessary. Subclasses are also responsible for storing and retrieving cookies from a file or database.
policy is an object implementing the CookiePolicy interface. For the other arguments, see the documentation for the corresponding attributes.
A CookieJar which can load cookies from, and perhaps save cookies to, a file on disk. Cookies are NOT loaded from the named file until either the load() or revert() method is called. Subclasses of this class are documented in section FileCookieJar subclasses and co-operation with web browsers.
This class is responsible for deciding whether each cookie should be accepted from / returned to the server.
Constructor arguments should be passed as keyword arguments only. blocked_domains is a sequence of domain names that we never accept cookies from, nor return cookies to. allowed_domains if not None, this is a sequence of the only domains for which we accept and return cookies. For all other arguments, see the documentation for CookiePolicy and DefaultCookiePolicy objects.
DefaultCookiePolicy implements the standard accept / reject rules for Netscape and RFC 2965 cookies. By default, RFC 2109 cookies (ie. cookies received in a Set-Cookie header with a version cookie-attribute of 1) are treated according to the RFC 2965 rules. However, if RFC 2965 handling is turned off or rfc2109_as_netscape is True, RFC 2109 cookies are ‘downgraded’ by the CookieJar instance to Netscape cookies, by setting the version attribute of the Cookie instance to 0. DefaultCookiePolicy also provides some parameters to allow some fine-tuning of policy.
This class represents Netscape, RFC 2109 and RFC 2965 cookies. It is not expected that users of http.cookiejar construct their own Cookie instances. Instead, if necessary, call make_cookies() on a CookieJar instance.
See also
- Module urllib.request
- URL opening with automatic cookie handling.
- Module http.cookies
- HTTP cookie classes, principally useful for server-side code. The http.cookiejar and http.cookies modules do not depend on each other.
- http://wp.netscape.com/newsref/std/cookie_spec.html
- The specification of the original Netscape cookie protocol. Though this is still the dominant protocol, the ‘Netscape cookie protocol’ implemented by all the major browsers (and http.cookiejar) only bears a passing resemblance to the one sketched out in cookie_spec.html.
- RFC 2109 - HTTP State Management Mechanism
- Obsoleted by RFC 2965. Uses Set-Cookie with version=1.
- RFC 2965 - HTTP State Management Mechanism
- The Netscape protocol with the bugs fixed. Uses Set-Cookie2 in place of Set-Cookie. Not widely used.
- http://kristol.org/cookie/errata.html
- Unfinished errata to RFC 2965.
RFC 2964 - Use of HTTP State Management
20.22.1. CookieJar and FileCookieJar Objects
CookieJar objects support the iterator protocol for iterating over contained Cookie objects.
CookieJar has the following methods:
Add correct Cookie header to request.
If policy allows (ie. the rfc2965 and hide_cookie2 attributes of the CookieJar‘s CookiePolicy instance are true and false respectively), the Cookie2 header is also added when appropriate.
The request object (usually a urllib.request..Request instance) must support the methods get_full_url(), get_host(), get_type(), unverifiable(), get_origin_req_host(), has_header(), get_header(), header_items(), and add_unredirected_header(), as documented by urllib.request.
Extract cookies from HTTP response and store them in the CookieJar, where allowed by policy.
The CookieJar will look for allowable Set-Cookie and Set-Cookie2 headers in the response argument, and store cookies as appropriate (subject to the CookiePolicy.set_ok() method’s approval).
The response object (usually the result of a call to urllib.request.urlopen(), or similar) should support an info() method, which returns a email.message.Message instance.
The request object (usually a urllib.request.Request instance) must support the methods get_full_url(), get_host(), unverifiable(), and get_origin_req_host(), as documented by urllib.request. The request is used to set default values for cookie-attributes as well as for checking that the cookie is allowed to be set.
Set the CookiePolicy instance to be used.
Return sequence of Cookie objects extracted from response object.
See the documentation for extract_cookies() for the interfaces required of the response and request arguments.
Set a Cookie if policy says it’s OK to do so.
Set a Cookie, without checking with policy to see whether or not it should be set.
Clear some cookies.
If invoked without arguments, clear all cookies. If given a single argument, only cookies belonging to that domain will be removed. If given two arguments, cookies belonging to the specified domain and URL path are removed. If given three arguments, then the cookie with the specified domain, path and name is removed.
Raises KeyError if no matching cookie exists.
Discard all session cookies.
Discards all contained cookies that have a true discard attribute (usually because they had either no max-age or expires cookie-attribute, or an explicit discard cookie-attribute). For interactive browsers, the end of a session usually corresponds to closing the browser window.
Note that the save() method won’t save session cookies anyway, unless you ask otherwise by passing a true ignore_discard argument.
FileCookieJar implements the following additional methods:
Save cookies to a file.
This base class raises NotImplementedError. Subclasses may leave this method unimplemented.
filename is the name of file in which to save cookies. If filename is not specified, self.filename is used (whose default is the value passed to the constructor, if any); if self.filename is None, ValueError is raised.
ignore_discard: save even cookies set to be discarded. ignore_expires: save even cookies that have expired
The file is overwritten if it already exists, thus wiping all the cookies it contains. Saved cookies can be restored later using the load() or revert() methods.
Load cookies from a file.
Old cookies are kept unless overwritten by newly loaded ones.
Arguments are as for save().
The named file must be in the format understood by the class, or LoadError will be raised. Also, IOError may be raised, for example if the file does not exist.
Clear all cookies and reload cookies from a saved file.
revert() can raise the same exceptions as load(). If there is a failure, the object’s state will not be altered.
FileCookieJar instances have the following public attributes:
Filename of default file in which to keep cookies. This attribute may be assigned to.
If true, load cookies lazily from disk. This attribute should not be assigned to. This is only a hint, since this only affects performance, not behaviour (unless the cookies on disk are changing). A CookieJar object may ignore it. None of the FileCookieJar classes included in the standard library lazily loads cookies.
20.22.2. FileCookieJar subclasses and co-operation with web browsers
The following CookieJar subclasses are provided for reading and writing .
A FileCookieJar that can load from and save cookies to disk in the Mozilla cookies.txt file format (which is also used by the Lynx and Netscape browsers).
Note
This loses information about RFC 2965 cookies, and also about newer or non-standard cookie-attributes such as port.
Warning
Back up your cookies before saving if you have cookies whose loss / corruption would be inconvenient (there are some subtleties which may lead to slight changes in the file over a load / save round-trip).
Also note that cookies saved while Mozilla is running will get clobbered by Mozilla.
A FileCookieJar that can load from and save cookies to disk in format compatible with the libwww-perl library’s Set-Cookie3 file format. This is convenient if you want to store cookies in a human-readable file.
20.22.3. CookiePolicy Objects
Objects implementing the CookiePolicy interface have the following methods:
Return boolean value indicating whether cookie should be accepted from server.
cookie is a Cookie instance. request is an object implementing the interface defined by the documentation for CookieJar.extract_cookies().
Return boolean value indicating whether cookie should be returned to server.
cookie is a Cookie instance. request is an object implementing the interface defined by the documentation for CookieJar.add_cookie_header().
Return false if cookies should not be returned, given cookie domain.
This method is an optimization. It removes the need for checking every cookie with a particular domain (which might involve reading many files). Returning true from domain_return_ok() and path_return_ok() leaves all the work to return_ok().
If domain_return_ok() returns true for the cookie domain, path_return_ok() is called for the cookie path. Otherwise, path_return_ok() and return_ok() are never called for that cookie domain. If path_return_ok() returns true, return_ok() is called with the Cookie object itself for a full check. Otherwise, return_ok() is never called for that cookie path.
Note that domain_return_ok() is called for every cookie domain, not just for the request domain. For example, the function might be called with both ".example.com" and "www.example.com" if the request domain is "www.example.com". The same goes for path_return_ok().
The request argument is as documented for return_ok().
Return false if cookies should not be returned, given cookie path.
See the documentation for domain_return_ok().
In addition to implementing the methods above, implementations of the CookiePolicy interface must also supply the following attributes, indicating which protocols should be used, and how. All of these attributes may be assigned to.
Implement Netscape protocol.
Implement RFC 2965 protocol.
Don’t add Cookie2 header to requests (the presence of this header indicates to the server that we understand RFC 2965 cookies).
The most useful way to define a CookiePolicy class is by subclassing from DefaultCookiePolicy and overriding some or all of the methods above. CookiePolicy itself may be used as a ‘null policy’ to allow setting and receiving any and all cookies (this is unlikely to be useful).
20.22.4. DefaultCookiePolicy Objects
Implements the standard rules for accepting and returning cookies.
Both RFC 2965 and Netscape cookies are covered. RFC 2965 handling is switched off by default.
The easiest way to provide your own policy is to override this class and call its methods in your overridden implementations before adding your own additional checks:
import http.cookiejar
class MyCookiePolicy(http.cookiejar.DefaultCookiePolicy):
def set_ok(self, cookie, request):
if not http.cookiejar.DefaultCookiePolicy.set_ok(self, cookie, request):
return False
if i_dont_want_to_store_this_cookie(cookie):
return False
return True
In addition to the features required to implement the CookiePolicy interface, this class allows you to block and allow domains from setting and receiving cookies. There are also some strictness switches that allow you to tighten up the rather loose Netscape protocol rules a little bit (at the cost of blocking some benign cookies).
A domain blacklist and whitelist is provided (both off by default). Only domains not in the blacklist and present in the whitelist (if the whitelist is active) participate in cookie setting and returning. Use the blocked_domains constructor argument, and blocked_domains() and set_blocked_domains() methods (and the corresponding argument and methods for allowed_domains). If you set a whitelist, you can turn it off again by setting it to None.
Domains in block or allow lists that do not start with a dot must equal the cookie domain to be matched. For example, "example.com" matches a blacklist entry of "example.com", but "www.example.com" does not. Domains that do start with a dot are matched by more specific domains too. For example, both "www.example.com" and "www.coyote.example.com" match ".example.com" (but "example.com" itself does not). IP addresses are an exception, and must match exactly. For example, if blocked_domains contains "192.168.1.2" and ".168.1.2", 192.168.1.2 is blocked, but 193.168.1.2 is not.
DefaultCookiePolicy implements the following additional methods:
Return the sequence of blocked domains (as a tuple).
Set the sequence of blocked domains.
Return whether domain is on the blacklist for setting or receiving cookies.
Return None, or the sequence of allowed domains (as a tuple).
Set the sequence of allowed domains, or None.
Return whether domain is not on the whitelist for setting or receiving cookies.
DefaultCookiePolicy instances have the following attributes, which are all initialised from the constructor arguments of the same name, and which may all be assigned to.
If true, request that the CookieJar instance downgrade RFC 2109 cookies (ie. cookies received in a Set-Cookie header with a version cookie-attribute of 1) to Netscape cookies by setting the version attribute of the Cookie instance to 0. The default value is None, in which case RFC 2109 cookies are downgraded if and only if RFC 2965 handling is turned off. Therefore, RFC 2109 cookies are downgraded by default.
General strictness switches:
Don’t allow sites to set two-component domains with country-code top-level domains like .co.uk, .gov.uk, .co.nz.etc. This is far from perfect and isn’t guaranteed to work!
RFC 2965 protocol strictness switches:
Follow RFC 2965 rules on unverifiable transactions (usually, an unverifiable transaction is one resulting from a redirect or a request for an image hosted on another site). If this is false, cookies are never blocked on the basis of verifiability
Netscape protocol strictness switches:
apply RFC 2965 rules on unverifiable transactions even to Netscape cookies
Flags indicating how strict to be with domain-matching rules for Netscape cookies. See below for acceptable values.
Ignore cookies in Set-Cookie: headers that have names starting with '$'.
Don’t allow setting cookies whose path doesn’t path-match request URI.
strict_ns_domain is a collection of flags. Its value is constructed by or-ing together (for example, DomainStrictNoDots|DomainStrictNonDomain means both flags are set).
When setting cookies, the ‘host prefix’ must not contain a dot (eg. www.foo.bar.com can’t set a cookie for .bar.com, because www.foo contains a dot).
Cookies that did not explicitly specify a domain cookie-attribute can only be returned to a domain equal to the domain that set the cookie (eg. spam.example.com won’t be returned cookies from example.com that had no domain cookie-attribute).
When setting cookies, require a full RFC 2965 domain-match.
The following attributes are provided for convenience, and are the most useful combinations of the above flags:
Equivalent to 0 (ie. all of the above Netscape domain strictness flags switched off).
Equivalent to DomainStrictNoDots|DomainStrictNonDomain.
20.22.5. Cookie Objects
Cookie instances have Python attributes roughly corresponding to the standard cookie-attributes specified in the various cookie standards. The correspondence is not one-to-one, because there are complicated rules for assigning default values, because the max-age and expires cookie-attributes contain equivalent information, and because RFC 2109 cookies may be ‘downgraded’ by http.cookiejar from version 1 to version 0 (Netscape) cookies.
Assignment to these attributes should not be necessary other than in rare circumstances in a CookiePolicy method. The class does not enforce internal consistency, so you should know what you’re doing if you do that.
Integer or None. Netscape cookies have version 0. RFC 2965 and RFC 2109 cookies have a version cookie-attribute of 1. However, note that http.cookiejar may ‘downgrade’ RFC 2109 cookies to Netscape cookies, in which case version is 0.
Cookie name (a string).
Cookie value (a string), or None.
String representing a port or a set of ports (eg. ‘80’, or ‘80,8080’), or None.
Cookie path (a string, eg. '/acme/rocket_launchers').
True if cookie should only be returned over a secure connection.
Integer expiry date in seconds since epoch, or None. See also the is_expired() method.
True if this is a session cookie.
String comment from the server explaining the function of this cookie, or None.
URL linking to a comment from the server explaining the function of this cookie, or None.
True if this cookie was received as an RFC 2109 cookie (ie. the cookie arrived in a Set-Cookie header, and the value of the Version cookie-attribute in that header was 1). This attribute is provided because http.cookiejar may ‘downgrade’ RFC 2109 cookies to Netscape cookies, in which case version is 0.
True if a port or set of ports was explicitly specified by the server (in the Set-Cookie / Set-Cookie2 header).
True if a domain was explicitly specified by the server.
True if the domain explicitly specified by the server began with a dot ('.').
Cookies may have additional non-standard cookie-attributes. These may be accessed using the following methods:
Return true if cookie has the named cookie-attribute.
If cookie has the named cookie-attribute, return its value. Otherwise, return default.
Set the value of the named cookie-attribute.
The Cookie class also defines the following method:
True if cookie has passed the time at which the server requested it should expire. If now is given (in seconds since the epoch), return whether the cookie has expired at the specified time.
20.22.6. Examples
The first example shows the most common usage of http.cookiejar:
import http.cookiejar, urllib.request
cj = http.cookiejar.CookieJar()
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")
This example illustrates how to open a URL using your Netscape, Mozilla, or Lynx cookies (assumes Unix/Netscape convention for location of the cookies file):
import os, http.cookiejar, urllib.request
cj = http.cookiejar.MozillaCookieJar()
cj.load(os.path.join(os.environ["HOME"], ".netscape/cookies.txt"))
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")
The next example illustrates the use of DefaultCookiePolicy. Turn on RFC 2965 cookies, be more strict about domains when setting and returning Netscape cookies, and block some domains from setting cookies or having them returned:
import urllib.request
from http.cookiejar import CookieJar, DefaultCookiePolicy
policy = DefaultCookiePolicy(
rfc2965=True, strict_ns_domain=Policy.DomainStrict,
blocked_domains=["ads.net", ".ads.net"])
cj = CookieJar(policy)
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")