如何修复管理器无法通过Words实例访问错误？

Question

我想要求和所有对象(freq)名称，当我执行这段代码时，它不工作，但相反，它引发了这个错误:管理器不能通过Words实例访问

我后来真的明白了这个错误是什么意思，但我不能把解决方案。我只知道有一个叫做(aggregate)的函数，但是我不能使用它，因为我需要从执行中排除一个特定的查询。

代码是这样的:

models.py

class Words(models.Model):
freq = models.IntegerField(blank=True, null=True)
...
def sum_freq(self):
freqs = []
words = self.objects.all().exclude(tag='Pu')
for word in words:
freqs.append(word.freq)
summation = sum(freqs)
return summation

def percent_n(self):
words = self.objects.all().exclude(tag='Pu')
percent_list = []
for word in words:
percent_n = (word.freq / word.sum_freq) * 100
percent_n = round(percent_n, 2)
percent_list.append(percent_n)
return percent_list

我需要先将freq查询求和，然后返回给percent_n函数，从而将sum_freq调用到percent_n中。直到现在我才知道percent_n函数是否有效，因为我没有测试freq函数。

Answer 1

您不应该使用self.objects，而是Words.objects或type(self).objects:

class Words(models.Model):
# …
def sum_freq(self):
freqs = []
words =type(self).objects.all().exclude(tag='Pu')
for word in words:
freqs.append(word.freq)
summation = sum(freqs)
return summation
def percent_n(self):
words =type(self).objects.all().exclude(tag='Pu')
percent_list = []
for word in words:
percent_n = (word.freq / word.sum_freq) * 100
percent_n = round(percent_n, 2)
percent_list.append(percent_n)
return percent_list

由于sum_freq和percent_n从来没有真正处理过self对象，您可能希望通过使用@classmethod装饰器将其转换为classmethod:

class Words(models.Model):
# …
@classmethod
def sum_freq(cls):
freqs = []
words =cls.objects.exclude(tag='Pu')
for word in words:
freqs.append(word.freq)
summation = sum(freqs)
return summation
@classmethod
def percent_n(cls):
words =cls.objects.exclude(tag='Pu')
percent_list = []
for word in words:
percent_n = (word.freq / word.sum_freq) * 100
percent_n = round(percent_n, 2)
percent_list.append(percent_n)
return percent_list

也就是说，你不需要自己聚合，你可以很容易地使用Django的.aggregate(…)进行聚合。[Django-doc]:

from django.db.models importF, Sum
from django.db.models.functions importRound
class Words(models.Model):
# …
@classmethod
def sum_freq(cls):
returncls.objects.exclude(tag='Pu').aggregate(
summation=Sum('freq')
)['summation'] or 0
@classmethod
def percent_n(cls):
summation = cls.sum_freq()
return list(
cls.objects.exclude(tag='Pu').values_list(
Round(10000*F('freq')/summation)/100,
flat=True
)
)