关于python：如何在django oscar的策略中应用可变税？

How to apply variable taxes in a Strategy in django oscar?

我正在为印度的奥斯卡项目工作，现在我想对产品征税。我已经跟踪了有关价格和可用性的税务申请文档，这是合作伙伴应用程序的分支。当我指定税率=('0.20')时，它对所有产品征收20%的税，现在我想使其具有动态性。

所以我浏览了strategy.fixedRateTax的代码，并尝试实现get_rate()的代码，因为它会被调用所有产品。

我想让它动态化的方法是，基于产品类别，我想对GeT_Rate()中的产品征税。

所以我在core/models.py中创建了一个模型。

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class CategoryTax(models.Model):
category = models.OneToOneField(Category, on_delete=models.CASCADE, unique=True)
gst_tax = models.DecimalField(max_digits=11, decimal_places=4, null=True, default=0)

def __str__(self):
return"%s" % self.category

在这里，类别模型的导入工作正常，但是当我转到strategy.py并从core和其他应用程序导入模型时，Django给出了一个例外。

我的forked_apps/partner/strategy.py是：

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from decimal import Decimal as D
from oscar.apps.partner import strategy, prices
from django.conf import settings

from oscar.core.loading import get_model
from core.models import CategoryTax

Partner = get_model('partner', 'Partner')
Category = get_model('catalogue', 'Category')
Product = get_model('catalogue', 'Product')
ProductCategory = get_model('catalogue', 'ProductCategory')

class Selector(object):
"""
Custom selector to return a India-specific strategy that charges GST
"""

def strategy(self, request=None, user=None, **kwargs):
return IndiaStrategy()

class IncludingVAT(strategy.FixedRateTax):
"""
Price policy to charge VAT on the base price
"""
# We can simply override the tax rate on the core FixedRateTax. Note
# this is a simplification: in reality, you might want to store tax
# rates and the date ranges they apply in a database table. Your
# pricing policy could simply look up the appropriate rate.

# The Tax rate applied here is 3 % GST Now
rate = D(settings.SITE_GST)

def get_rate(self, product, stockrecord):
"""
This method serves as hook to be able to plug in support for varying tax rates
based on the product.

TODO: Needs tests.
"""

try:
product = Product.objects.get(id=product.id)
prod_cat = ProductCategory.objects.get(product=product)
cat = Category.objects.get(id=prod_cat.category_id)

cat_tax = CategoryTax.objects.get(category=cat)
print("The Cat Tax:", cat_tax)

except Exception as e:
print(e)
return self.rate
class IndiaStrategy(strategy.UseFirstStockRecord, IncludingVAT,
strategy.StockRequired, strategy.Structured):
"""
Typical India strategy for physical goods.

- There's only one warehouse/partner so we use the first and only stockrecord
- Enforce stock level. Don't allow purchases when we don't have stock.
- Charge Indian GST on prices. Assume everything is standard-rated.
"""

我得到的例外是：

1	django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

还有：ImportError: cannot import name 'CategoryTax'。

一定要建议我用任何可能的方法来完成这项工作。

我用的是django 2.1.3，django oscar 1.6.4

整个错误堆栈跟踪：

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Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x7f623e655400>
Traceback (most recent call last):
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 296, in get_model
return apps.get_model(app_label, model_name)
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 195, in get_model
self.check_models_ready()
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 137, in check_models_ready
raise AppRegistryNotReady("Models aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 296, in get_model
return apps.get_model(app_label, model_name)
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 195, in get_model
self.check_models_ready()
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 137, in check_models_ready
raise AppRegistryNotReady("Models aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File"/home/venvs/test/lib/python3.6/site-packages/django/utils/autoreload.py", line 225, in wrapper
fn(*args, **kwargs)
File"/home/test/abhushan/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
autoreload.raise_last_exception()
File"/home/venvs/test/lib/python3.6/site-packages/django/utils/autoreload.py", line 248, in raise_last_exception
raise _exception[1]
File"/home/venvs/test/lib/python3.6/site-packages/django/core/management/__init__.py", line 337, in execute
autoreload.check_errors(django.setup)()
File"/home/venvs/test/lib/python3.6/site-packages/django/utils/autoreload.py", line 225, in wrapper
fn(*args, **kwargs)
File"/home/venvs/test/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 112, in populate
app_config.import_models()
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/config.py", line 198, in import_models
self.models_module = import_module(models_module_name)
File"/home/venvs/test/lib/python3.6/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File"<frozen importlib._bootstrap>", line 994, in _gcd_import
File"<frozen importlib._bootstrap>", line 971, in _find_and_load
File"<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
File"<frozen importlib._bootstrap>", line 665, in _load_unlocked
File"<frozen importlib._bootstrap_external>", line 678, in exec_module
File"<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File"/home/venvs/test/project/core/models.py", line 8, in <module>
Category = get_model('catalogue', 'Category')
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 308, in get_model
import_module('%s.%s' % (app_config.name, MODELS_MODULE_NAME))
File"/home/venvs/test/lib/python3.6/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File"<frozen importlib._bootstrap>", line 994, in _gcd_import
File"<frozen importlib._bootstrap>", line 971, in _find_and_load
File"<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
File"<frozen importlib._bootstrap>", line 665, in _load_unlocked
File"<frozen importlib._bootstrap_external>", line 678, in exec_module
File"<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File"/home/venvs/test/lib/python3.6/site-packages/oscar/apps/catalogue/models.py", line 4, in <module>
from oscar.apps.catalogue.abstract_models import * # noqa
File"/home/venvs/test/lib/python3.6/site-packages/oscar/apps/catalogue/abstract_models.py", line 35, in <module>
Selector = get_class('partner.strategy', 'Selector')
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 59, in get_class
return get_classes(module_label, [classname], module_prefix)[0]
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 69, in get_classes
return class_loader(module_label, classnames, module_prefix)
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 141, in default_class_loader
local_module = _import_module(local_module_label, classnames)
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 182, in _import_module
return __import__(module_label, fromlist=classnames)
File"/home/test/forked_apps/partner/strategy.py", line 16, in <module>
Category = get_model('catalogue', 'Category')
File"/home/venvs/test/lib/python3.6/site-packages/oscar/core/loading.py", line 311, in get_model
return apps.get_registered_model(app_label, model_name)
File"/home/venvs/test/lib/python3.6/site-packages/django/apps/registry.py", line 270, in get_registered_model
"Model '%s.%s' not registered." % (app_label, model_name))
LookupError: Model 'catalogue.Category' not registered.