Issues with admin in django

I am making a shopping cart using mezzanine and cartridge.

In my order model there is a field called status which has choices of unprocessed and processed. After an order is placed an admin can change their status. I want to send an email to the user whenever an admin updates the status.

I have done some R&D on it but I didn't find anything which tells me how to send an email on change of status.

My model:

class Order(models.Model):
    ...
    ....
    ........
    status = models.IntegerField(_("Status"),
                            choices=settings.SHOP_ORDER_STATUS_CHOICES,
                            default=settings.SHOP_ORDER_STATUS_CHOICES[0][0])

    objects = managers.OrderManager()

    # These are fields that are stored in the session. They're copied to
    # the order in setup() and removed from the session in complete().
    session_fields = ("shipping_type", "shipping_total", "discount_total")

    class Meta:
        verbose_name = _("Order")
        verbose_name_plural = _("Orders")
        ordering = ("-id",)

    def __unicode__(self):
        return "#%s %s %s" % (self.id, self.billing_name(), self.time)

    def billing_name(self):
        return "%s %s" % (self.billing_detail_first_name,
                          self.billing_detail_last_name)



    def setup(self, request):

        self.key = request.session.session_key
        self.user_id = request.user.id
        for field in self.session_fields:
            if field in request.session:
                setattr(self, field, request.session[field])
        self.total = self.item_total = request.cart.total_price()
        if self.shipping_total is not None:
            self.shipping_total = Decimal(str(self.shipping_total))
            self.total += self.shipping_total
        if self.discount_total is not None:
            self.total -= self.discount_total
        self.save()  # We need an ID before we can add related items.
        for item in request.cart:
            product_fields = [f.name for f in SelectedProduct._meta.fields]
            item = dict([(f, getattr(item, f)) for f in product_fields])
            self.items.create(**item)

    def complete(self, request):

        self.save()  # Save the transaction ID.
        for field in self.session_fields:
            if field in request.session:
                del request.session[field]
        del request.session["order"]
        for item in request.cart:
            try:
                variation = ProductVariation.objects.get(sku=item.sku)
            except ProductVariation.DoesNotExist:
                pass
            else:
                variation.update_stock(item.quantity * -1)
                variation.product.actions.purchased()
        code = request.session.get('discount_code')
        if code:
            DiscountCode.objects.active().filter(code=code).update(
                uses_remaining=F('uses_remaining') - 1)
        request.cart.delete()

    def details_as_dict(self):

        context = {}
        for fieldset in ("billing_detail", "shipping_detail"):
            fields = [(f.verbose_name, getattr(self, f.name)) for f in
                self._meta.fields if f.name.startswith(fieldset)]
            context["order_%s_fields" % fieldset] = fields
        return context

Admin:

class OrderAdmin(admin.ModelAdmin):
    ordering = ("status", "-id")
    list_display = ("id", "billing_name", "total", "time", "status",
                    "transaction_id", "invoice")
    list_editable = ("status",)
    list_filter = ("status", "time")
    list_display_links = ("id", "billing_name",)
    search_fields = (["id", "status", "transaction_id"] +
                     billing_fields + shipping_fields)
    date_hierarchy = "time"
    radio_fields = {"status": admin.HORIZONTAL}
    inlines = (OrderItemInline,)
    formfield_overrides = {MoneyField: {"widget": MoneyWidget}}
    fieldsets = (
        (_("Billing details"), {"fields": (tuple(billing_fields),)}),
        (_("Shipping details"), {"fields": (tuple(shipping_fields),)}),
        (None, {"fields": ("additional_instructions", ("shipping_total",
            "shipping_type"), ("discount_total", "discount_code"),
            "item_total", ("total", "status"), "transaction_id")}),
    )
admin.site.register(Order, OrderAdmin)

Can anybody please tell me how I can send this email?

You need to add a listener on the post_save signal for the model. Your listener (which is a standard Python method) will check what field has changed and then dispatch the email to the user.