gistfile1.py

from django import http
import operator
import pickle

def copy_pickleable(a, b):
    for k, v in a.iteritems():
        try:
            pickle.dumps(v)
            b[k] = v
        except TypeError:
            pass

def generator_view(gen):
    def wrapped(request):
        if gen.__name__ in request.session:
            g = pickle.loads(request.session[gen.__name__])
        else:
            g = gen()
            g.next()

        mockreq = http.HttpRequest()
        copy_pickleable(request.__dict__, mockreq.__dict__)
        mockreq.POST = {}
        copy_pickleable(request.POST, mockreq.POST)
        mockreq.GET = {}
        copy_pickleable(request.GET, mockreq.GET)
        mockreq.META = {}
        copy_pickleable(request.META, mockreq.META)

        response = g.send(mockreq)
        request.session[gen.__name__] = pickle.dumps(g)
        return response
    return wrapped

@generator_view
def calc():
    request = (yield)
    while True:
        op = None
        while not op:
            request = yield http.HttpResponse("""
            <form method="POST">
            <p>Operator:</p>
            <p><input type="radio" name="operator" value="add" /> Add</p>
            <p><input type="radio" name="operator" value="sub" /> Subtract</p>
            <p><input type="radio" name="operator" value="mul" /> Multiply</p>
            <p><input type="radio" name="operator" value="div" /> Divide</p>
            <input type="submit" />
            </form>
            """)
            if request.method == "POST" and "operator" in request.POST:
                op = getattr(operator, request.POST["operator"], None)

        symbol = ({
            operator.add: "+",
            operator.sub: "-",
            operator.div: "/",
            operator.mul: "*"
        }[op])

        first = None
        while not first:
            request = yield http.HttpResponse("""
            <form method="POST">
            <p>First operand:</p>
            <p><input type="text" name="first" /></p>
            <input type="submit" />
            </form>
            """)
            if request.method == "POST":
                try:
                    first = int(request.POST["first"])
                except ValueError:
                    pass

        second = None
        while not second:
            request = yield http.HttpResponse("""
            <form method="POST">
            <p>Second operand:</p>
            <p><input type="text" name="second" /></p>
            <input type="submit" />
            </form>
            """)
            if request.method == "POST":
                try:
                    second = int(request.POST["second"])
                except ValueError:
                    pass

        request = yield http.HttpResponse("""
        <p>%(first)s %(symbol)s %(second)s = %(result)s</p>
        <p><a href=".">Back</a></p>
        """ % {
            "first": first,
            "second": second,
            "result": op(first, second),
            "symbol": symbol
        })