在python中如何檢查對象是否具有值？

Question

基本賬戶

class BaseAccount(models.Model):
user = models.ForeignKey(User, unique=True)

def __unicode__(self):
    """
    Return the unicode representation of this customer, which is the user's
    full name, if set, otherwise, the user's username
    """
    fn = self.user.get_full_name()
    if fn:
        return fn
    return self.user.username

def user_name(self):
    """
    Returns the full name of the related user object
    """
    return self.user.get_full_name()

def email(self):
    """
    Return the email address of the related user object
    """
    return self.user.email

def is_store(self):
    #try:
    #   self.user.is_store
    #    return True
    #except ObjectDoesNotExist:
    #    return False
    return self.user.is_store

def is_professional(self):
    try:
        self.user.is_professional
        return True
    except ObjectDoesNotExist:
        return False

帳戶類別

class Account(BaseAccount):
    """
    The account is an extension of the Django user and serves as the profile
    object in user.get_profile() for shop purchases and sessions
    """
    telephone = models.CharField(max_length=32)
    default_address = models.ForeignKey(Address, related_name='billing_account', blank=True, null=True)
    security_question = models.ForeignKey(SecurityQuestion)
    security_answer = models.CharField(max_length=200)
    how_heard = models.CharField("How did you hear about us?", max_length=100)
    feedback = models.TextField(blank=True)
    opt_in = models.BooleanField("Subscribe to mailing list", help_text="Please tick here if you would like to receive updates from %s" % Site.objects.get_current().name)
    temporary = models.BooleanField()

 def has_placed_orders(self):
     """
     Returns True if the user has placed at least one order, False otherwise
     """
     return self.order_set.count() > 0

 def get_last_order(self):
     """
     Returns the latest order that this customer has placed. If no orders
     have been placed, then None is returned
     """
     try:
         return self.order_set.all().order_by('-date')[0]
     except IndexError:
         return None

 def get_currency(self):
     """
     Get the currency for this customer. If global currencies are enabled
     (settings.ENABLE_GLOBAL_CURRENCIES) then this function will return
     the currency related to their default address, otherwise, it returns
     the site default
     """
     if settings.ENABLE_GLOBAL_CURRENCIES:
         return self.default_address.country.currency
     return Currency.get_default_currency()
 currency = property(get_currency)

 def get_gateway_currency(self):
     """
     Get the currency that an order will be put through protx with. If protx
     currencies are enabled (settings.ENABLE_PROTX_CURRENCIES), then the
     currency will be the same returned by get_currency, otherwise, the
     site default is used
     """
     if settings.ENABLE_PROTX_CURRENCIES and settings.ENABLE_GLOBAL_CURRENCIES:
         return self.currency
     return Currency.get_default_currency()
 gateway_currency = property(get_gateway_currency)

地址類別

class Address(models.Model):
"""
This class encapsulates the data required for postage and payment mechanisms
across the site. Each address is associated with a single store account
"""
trade_user = models.BooleanField("Are you a stockist of Neal & Wolf Products", help_text="Please here if you are a Neal & Wolf Stockist")
company_name = models.CharField(max_length=32, blank=True)
line1 = models.CharField(max_length=200)
line2 = models.CharField(max_length=200, blank=True)
line3 = models.CharField(max_length=200, blank=True)
city = models.CharField(max_length=32)
county = models.CharField(max_length=32)
postcode = models.CharField(max_length=12)
country = models.ForeignKey(Country)
account = models.ForeignKey('Account')

class Meta:
    """
    Django meta options

    verbose_name_plural = "Addresses"
    """
    verbose_name_plural = "Addresses"

def __unicode__(self):
    """
    The unicode representation of this address, the postcode plus the county
    """
    return ', '.join((self.postcode, str(self.county)))

def line_list(self):
    """
    Return a list of all of this objects address lines that are not blank,
    in the natural order that you'd expect to see them. This is useful for
    outputting to a template with the aid of python String.join()
    """
    return [val for val in (self.line1, self.line2, self.line3, self.city, self.county, self.postcode, self.country.name) if val]

關於查看三個類，我的問題很簡單，我如何確定用戶是否為交易用戶（此值收集在Address類中）

謝謝

Answer 1

如果Account類是您的用戶個人資料（如其文檔字符串所示），那么您應該能夠執行以下操作：

is_trade_user = user.get_profile().default_address.trade_user

如果貿易用戶的定義是“具有一個trade_user為true的默認地址”

另一方面，如果貿易用戶的定義為“具有trade_user為true的任何地址”，那么您將需要做一些更復雜的事情-檢查所有地址，如果其中任何一個設置了trade_user，則返回true：

is_trade_user = user.get_profile().address_set.filter(trade_user=True).count() > 0