Request for elucidation: enhanced generators

[Michele Simionato]

Ben Sizer wrote:
> But do you have an example of such a use case?

Here is a 69 lines implementation of the idea of applying extended
generators to manage Web forms (obviously this is only a proof of
concept and it contains many mistakes, but you have something to get
started).
Notice that I am not claiming that this is a good idea.

  Michele Simionato

---

import datetime
import cherrypy as cp

# each user (but really should be each session) has her input loop
# one should disable the back button and implement an undo mechanism
def inputloop(user):
    start_time = datetime.datetime.today()
    cart = []
    while True: # fill the shopping cart
        item = yield locals()
        if item == 'start':
            continue
        elif item == 'end':
            break
        elif item:
            cart.append(item)
    finish_time = datetime.datetime.today()
    yield locals()

class User(object):
    def __init__(self, name):
        self.name = name
        self.inputloop = inputloop(self)
        self.inputloop.send(None) # start the user loop

users = dict(michele=User('michele'))

class Root(object):
    @cp.expose
    def login_welcome(self):
        yield 'hello!'
        yield '<form action="login_action">'
        yield "what's your name? "
        yield '<input type="text" name="name"/>'
        yield '</form>'

    @cp.expose
    def login_action(self, name):
        yield ('<a href="shopping_loop?name=%s&item=start">'
               'You may start shopping</a><br/>') % name

    @cp.expose
    def shopping_loop(self, name, item):
        if not name in users:
            yield '%r is not a valid name; please retry' % name
            return
        user = users[name]
        status  = user.inputloop.send(item)
        if item == 'start':
            yield 'Today is %s<br/>' % status['start_time']
            yield 'Please buy something!<br/>'
        if item == 'end':
            yield 'Thanks for shopping, %s<br/>' % user.name
            yield 'You bought items %s<br/>' % status['cart']
            yield 'Today is %s' % status['finish_time']
            return
        yield '<form action="">'
        yield 'The content of your cart is %s<br/>' % status['cart']
        yield 'Please enter the item you want to buy: '
        yield '<input type="text" name="item"/><br/>'
        yield '<input type="hidden" name="name" value="%s"/>' % name
        yield '(enter end to finish)'
        yield '</form>'

    index = login_welcome

if __name__ == '__main__':
    cp.root = Root()
    cp.server.start()