openwpm.utilities.cookie module

Here’s a sample session to show how to use this module. At the moment, this is the only documentation.

The Basics

Importing is easy..

>>> import Cookie

Most of the time you start by creating a cookie. Cookies come in three flavors, each with slightly different encoding semantics, but more on that later.

>>> C = Cookie.SimpleCookie()
>>> C = Cookie.SerialCookie()
>>> C = Cookie.SmartCookie()

[Note: Long-time users of Cookie.py will remember using Cookie.Cookie() to create a Cookie object. Although deprecated, it is still supported by the code. See the Backward Compatibility notes for more information.]

Once you’ve created your Cookie, you can add values just as if it were a dictionary.

>>> C = Cookie.SmartCookie()
>>> C["fig"] = "newton"
>>> C["sugar"] = "wafer"
>>> C.output()
'Set-Cookie: fig=newton\r\nSet-Cookie: sugar=wafer'

Notice that the printable representation of a Cookie is the appropriate format for a Set-Cookie: header. This is the default behavior. You can change the header and printed attributes by using the .output() function

>>> C = Cookie.SmartCookie()
>>> C["rocky"] = "road"
>>> C["rocky"]["path"] = "/cookie"
>>> print C.output(header="Cookie:")
Cookie: rocky=road; Path=/cookie
>>> print C.output(attrs=[], header="Cookie:")
Cookie: rocky=road

The load() method of a Cookie extracts cookies from a string. In a CGI script, you would use this method to extract the cookies from the HTTP_COOKIE environment variable.

>>> C = Cookie.SmartCookie()
>>> C.load("chips=ahoy; vienna=finger")
>>> C.output()
'Set-Cookie: chips=ahoy\r\nSet-Cookie: vienna=finger'

The load() method is darn-tootin smart about identifying cookies within a string. Escaped quotation marks, nested semicolons, and other such trickeries do not confuse it.

>>> C = Cookie.SmartCookie()
>>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";')
>>> print C
Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;"

Each element of the Cookie also supports all of the RFC 2109 Cookie attributes. Here’s an example which sets the Path attribute.

>>> C = Cookie.SmartCookie()
>>> C["oreo"] = "doublestuff"
>>> C["oreo"]["path"] = "/"
>>> print C
Set-Cookie: oreo=doublestuff; Path=/

Each dictionary element has a ‘value’ attribute, which gives you back the value associated with the key.

>>> C = Cookie.SmartCookie()
>>> C["twix"] = "none for you"
>>> C["twix"].value
'none for you'

A Bit More Advanced

As mentioned before, there are three different flavors of Cookie objects, each with different encoding/decoding semantics. This section briefly discusses the differences.

SimpleCookie

The SimpleCookie expects that all values should be standard strings. Just to be sure, SimpleCookie invokes the str() builtin to convert the value to a string, when the values are set dictionary-style.

>>> C = Cookie.SimpleCookie()
>>> C["number"] = 7
>>> C["string"] = "seven"
>>> C["number"].value
'7'
>>> C["string"].value
'seven'
>>> C.output()
'Set-Cookie: number=7\r\nSet-Cookie: string=seven'

SerialCookie

The SerialCookie expects that all values should be serialized using cPickle (or pickle, if cPickle isn’t available). As a result of serializing, SerialCookie can save almost any Python object to a value, and recover the exact same object when the cookie has been returned. (SerialCookie can yield some strange-looking cookie values, however.)

>>> C = Cookie.SerialCookie()
>>> C["number"] = 7
>>> C["string"] = "seven"
>>> C["number"].value
7
>>> C["string"].value
'seven'
>>> C.output()
'Set-Cookie: number="I7\\012."\r\nSet-Cookie: string="S\'seven\'\\012p1\\012."'  # noqa

Be warned, however, if SerialCookie cannot de-serialize a value (because it isn’t a valid pickle’d object), IT WILL RAISE AN EXCEPTION.

SmartCookie

The SmartCookie combines aspects of each of the other two flavors. When setting a value in a dictionary-fashion, the SmartCookie will serialize (ala cPickle) the value if and only if it isn’t a Python string. String objects are not serialized. Similarly, when the load() method parses out values, it attempts to de-serialize the value. If it fails, then it fallsback to treating the value as a string.

>>> C = Cookie.SmartCookie()
>>> C["number"] = 7
>>> C["string"] = "seven"
>>> C["number"].value
7
>>> C["string"].value
'seven'
>>> C.output()
'Set-Cookie: number="I7\\012."\r\nSet-Cookie: string=seven'

Backwards Compatibility

In order to keep compatibilty with earlier versions of Cookie.py, it is still possible to use Cookie.Cookie() to create a Cookie. In fact, this simply returns a SmartCookie.

>>> C = Cookie.Cookie()
>>> print C.__class__.__name__
SmartCookie

Finis.

class openwpm.utilities.cookie.BaseCookie(input=None)

Bases: dict

js_output(attrs=None)

Return a string suitable for JavaScript.

load(rawdata)

Load cookies from a string (presumably HTTP_COOKIE) or from a dictionary. Loading cookies from a dictionary ‘d’ is equivalent to calling:

map(Cookie.__setitem__, d.keys(), d.values())

output(attrs=None, header='Set-Cookie:', sep='\r\n')

Return a string suitable for HTTP.

value_decode(val)

real_value, coded_value = value_decode(STRING) Called prior to setting a cookie’s value from the network representation. The VALUE is the value read from HTTP header. Override this function to modify the behavior of cookies.

value_encode(val)

real_value, coded_value = value_encode(VALUE) Called prior to setting a cookie’s value from the dictionary representation. The VALUE is the value being assigned. Override this function to modify the behavior of cookies.

openwpm.utilities.cookie.Cookie

alias of SmartCookie

exception openwpm.utilities.cookie.CookieError

Bases: Exception

class openwpm.utilities.cookie.SerialCookie(input=None)

Bases: BaseCookie

SerialCookie supports arbitrary objects as cookie values. All values are serialized (using cPickle) before being sent to the client. All incoming values are assumed to be valid Pickle representations. IF AN INCOMING VALUE IS NOT IN A VALID PICKLE FORMAT, THEN AN EXCEPTION WILL BE RAISED.

Note: Large cookie values add overhead because they must be retransmitted on every HTTP transaction.

Note: HTTP has a 2k limit on the size of a cookie. This class does not check for this limit, so be careful!!!

value_decode(val)

real_value, coded_value = value_decode(STRING) Called prior to setting a cookie’s value from the network representation. The VALUE is the value read from HTTP header. Override this function to modify the behavior of cookies.

value_encode(val)

real_value, coded_value = value_encode(VALUE) Called prior to setting a cookie’s value from the dictionary representation. The VALUE is the value being assigned. Override this function to modify the behavior of cookies.

class openwpm.utilities.cookie.SimpleCookie(input=None)

Bases: BaseCookie

SimpleCookie supports strings as cookie values. When setting the value using the dictionary assignment notation, SimpleCookie calls the builtin str() to convert the value to a string. Values received from HTTP are kept as strings.

value_decode(val)

real_value, coded_value = value_decode(STRING) Called prior to setting a cookie’s value from the network representation. The VALUE is the value read from HTTP header. Override this function to modify the behavior of cookies.

value_encode(val)

real_value, coded_value = value_encode(VALUE) Called prior to setting a cookie’s value from the dictionary representation. The VALUE is the value being assigned. Override this function to modify the behavior of cookies.

class openwpm.utilities.cookie.SmartCookie(input=None)

Bases: BaseCookie

SmartCookie supports arbitrary objects as cookie values. If the object is a string, then it is quoted. If the object is not a string, however, then SmartCookie will use cPickle to serialize the object into a string representation.

Note: Large cookie values add overhead because they must be retransmitted on every HTTP transaction.

Note: HTTP has a 2k limit on the size of a cookie. This class does not check for this limit, so be careful!!!

value_decode(val)

real_value, coded_value = value_decode(STRING) Called prior to setting a cookie’s value from the network representation. The VALUE is the value read from HTTP header. Override this function to modify the behavior of cookies.

value_encode(val)

real_value, coded_value = value_encode(VALUE) Called prior to setting a cookie’s value from the dictionary representation. The VALUE is the value being assigned. Override this function to modify the behavior of cookies.