import conservancy
def index(request):
partial_amount = conservancy.param_if_valid(request.GET, 'upgrade', 'upgrade_id', 0)
with conservancy.ParameterValidator(request.GET, 'upgrade_id') as validator:
try:
amount_param = float(request.GET['upgrade'])
except (KeyError, ValueError):
validator.fail()
else:
validator.validate('{.2f}'.format(amount_param))
partial_amount = amount_param if validator.valid else 0
context = {
'partial_amount': partial_amount,
'minimum_amount': 120 - partial_amount,