Karrigell/Set, read and erase cookies

Cookies are managed by two variables available in the scripts :

  • COOKIE is a dictionary-like object holding the cookies sent by the browser and received by the script
  • SET_COOKIE is a dictionary-like object used by the script to set cookies values, path, expiry date etc. and send them to the browser

Here is a simple script, cookies.py, that shows how to set, read and erase cookies :

def index(**kw):
    body = 'Received cookies'
    for cookie in COOKIE:
        body += BR()+B(cookie)+' '+COOKIE[cookie].value
        body += A('Erase',href="erase?name=%s" %cookie)
    form = FORM(action ="set_cookie",method="post")
    form <= 'Name'+INPUT(name="name")+BR()
    form <= 'Value' + INPUT(name="value")+BR()
    form <= INPUT(Type="submit",value="Ok")
    return HTML(BODY(body+form))
 
def set_cookie(name,value):
    SET_COOKIE[name] = value
    SET_COOKIE[name]['path'] = '/'
    raise HTTP_REDIRECTION('index')
 
def cookie_expiry_date(numdays): 
    """ Returns a cookie expiry date in the required format.
    `expires` should be a string in the format "Wdy, DD-Mon-YY HH:MM:SS GMT"
    """ 
    from datetime import date, timedelta 
    new = date.today() + timedelta(days = numdays) 
    return new.strftime("%a, %d-%b-%Y 23:59:59 GMT") 
 
def erase(name):
    SET_COOKIE[name] = ''
    SET_COOKIE[name]['path'] = '/'
    SET_COOKIE[name]['expires'] = cookie_expiry_date(-10)
    SET_COOKIE[name]['max-age'] = 0
    raise HTTP_REDIRECTION('index')

In index(), the cookies sent by the browser are printed. Then a form allows the user to set another cookie, with a specified name and value

This form is submitted to the function set_cookie(name,value). In this function, a new entry is created in SET_COOKIE with the submitted data. The key 'path' of this entry is set to the server root. Then a redirection is performed to the index() function

When this redirection is done, the newly created cookie is sent to the browser. The browser stores the value and its attribute ; then it sends a request to the url http://host/cookies.py/index

When this request is sent, the request headers include this cookie, received by the script in the variable COOKIE : so the cookie name and value are printed at the top of the page

To erase the cookie, a link is provided, leading to the function erase(name) where name is the cookie name. The function erase() uses SET_COOKIE to erase the value, and set the expiry date to the past (10 days before today), using the function cookie_expiry_date() to transform a datetime object to the format supported by the cookie specifications

At last, when these values are set for the cookie, another redirection is performed to index() : the browser receives the new information about the specified cookie. Since the expiry date is reached, it erases it. When it sends a request to http://host/cookies.py/index, it does not send a header for this cookie, which does not appear in the received cookies list

Last modified on 23 February 2011, at 14:01