在python中，如何查看对象是否具有值？ [英] In python how can I check to see if an object has a value?

问题描述

基础帐户

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

帐户类别

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)

地址类

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]

关于看到三个类我的问题很容易，我如何知道用户是否是一个交易用户（该值在地址类中收集）

About see three classes my question is easy how do i find out whether or not the user, is a trade user(this value is gathered in the Address class)

谢谢

推荐答案

如果帐户类是您的用户个人资料， docstring建议，那么你应该可以这样做：

If the Account class is your user profile, as its docstring suggests, then you should be able to do something like this:

is_trade_user = user.get_profile().default_address.trade_user

如果交易用户的定义是具有 trade_user的默认地址为真

if the definition of a trade user is "Has a default address for which trade_user is true"

另一方面，如果贸易用户的定义是Has 任何地址， trade_user 是真的th en你需要做一些更复杂的事情 - 检查所有的地址，并返回true，如果其中任何一个都有trade_user设置：

On the other hand, if the definition of trade user is "Has any address for which trade_user is true" then you will need to do something more complicated -- check all of the addresses, and return true if any of them have trade_user set:

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

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