我正在尝试使用django项目中通过faker生成的一些伪数据填充模型。我创建了三个模型Publisher，Author和Book。迁移正确完成，并且模型创建成功。我能够通过管理界面将数据添加到模型中，但是当我尝试通过假数据填充模型时，出现以下错误。django.db.utils.IntegrityError：NOT NULL约束失败：BookApp_book.publisher_id 我无法弄清楚这是什么错误。这是我的模型。py
from django.db import models
# Create your models here.
class Publisher(models.Model):
'''
Publisher class model with name,country,email,website
'''
name = models.CharField(max_length=25)
country = models.CharField(max_length=25)
website = models.URLField()
def __str__(self):
return self.name
class Author(models.Model):
'''
Author model with name,contact,email,age,location
'''
author_name = models.CharField(max_length=25)
age = models.PositiveSmallIntegerField()
email = models.EmailField()
# method for string representation of the class
def __str__(self):
return self.author_name
class Book(models.Model):
'''
Book model with title,pages,author,publisher,publication_date
'''
title = models.CharField(max_length=100)
pages = models.PositiveSmallIntegerField()
author = models.ManyToManyField('Author')
publisher = models.ForeignKey(Publisher,related_name='publisher',on_delete=models.CASCADE)
publication_date = models.DateField()
# method for string representation of book class
def __str__(self):
return self.title
populate_bookapp.py
import os
# set the default environment to the projects settings
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'BooksProject.settings')
import django
django.setup()
# faker popscript to populate the models with fake data
from faker import Faker
from BookApp.models import Publisher,Author,Book
import random
# create an object for faker
fake_gen = Faker()
titlelist = ['Impossible Spindle','Savage Vice','Shackle the future','Eden Grieving',
'Cloaked Grace','Crime of the Silent Baker','The Sulphur Earth',
'Snows of Jupiter','The Demon in the Window','Tapped for Duty']
# function to add the book titles
def add_title():
t = Book.objects.get_or_create(title = random.choice(titlelist))[0]
t.save()
return t
# function to populate the records into the models
def populate_records(N=5):
# for loop to generate the data
for entry in range(N):
# create fake names, urls, emails, companies, books, dates
fake_auth_name = fake_gen.name()
fake_country = fake_gen.country()
fake_website = fake_gen.url()
fake_comp = fake_gen.company()
fake_age = fake_gen.random_int(0,60)
fake_email = fake_gen.email()
fake_pages = fake_gen.random_int(0,500)
fake_date = fake_gen.date()
# add a publisher entry
pub = Publisher.objects.get_or_create(name=fake_comp,
country=fake_country,
website=fake_website)[0]
# add a author entry
auth = Author.objects.get_or_create(author_name=fake_auth_name,
age=fake_age,
email=fake_email)[0]
book_title = add_title()
# add book entry
bk_rec = Book.objects.get_or_create(title=book_title,
pages=fake_pages,author=auth,
publisher=pub,
publication_date=fake_date)[0]
# Add records to the models
if __name__ == '__main__':
print('Populating started')
populate_records(10)
print('Finished')
错误回溯
Populating started
Traceback (most recent call last):
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 538, in get_or_create
return self.get(**kwargs), False
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 406, in get
raise self.model.DoesNotExist(
BookApp.models.DoesNotExist: Book matching query does not exist.
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\sqlite3\base.py", line 383, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: NOT NULL constraint failed: BookApp_book.pages
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "populate_bookapp.py", line 62, in <module>
populate_records(10)
File "populate_bookapp.py", line 52, in populate_records
book_title = add_title()
File "populate_bookapp.py", line 22, in add_title
t = Book.objects.get_or_create(title = random.choice(titlelist))[0]
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\manager.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 541, in get_or_create
return self._create_object_from_params(kwargs, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 583, in _create_object_from_params
raise e
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 575, in _create_object_from_params
obj = self.create(**params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 422, in create
obj.save(force_insert=True, using=self.db)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\base.py", line 740, in save
self.save_base(using=using, force_insert=force_insert,
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\base.py", line 777, in save_base
updated = self._save_table(
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\base.py", line 870, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\base.py", line 907, in _do_insert
return manager._insert([self], fields=fields, return_id=update_pk,
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\manager.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\models\query.py", line 1186, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-p
ackages\django\db\models\sql\compiler.py", line 1335, in execute_sql
cursor.execute(sql, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 99, in execute
return super().execute(sql, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 67, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 76, in _execute_with_wrappers
return executor(sql, params, many, context)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-packages\django\db\utils.py",
line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "C:\Users\Gururaj Deshpande\Anaconda3\envs\MyDjangoEnv\lib\site-
packages\django\db\backends\sqlite3\base.py", line 383, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: BookApp_book.pages
查看您的错误跟踪，它可以准确告诉您错误发生在哪里以及它是什么：
File "populate_bookapp.py", line 22, in add_title
t = Book.objects.get_or_create(title = random.choice(titlelist))[0]
您要在此处创建没有pages和没有publisher的书。 NOT NULL constraint failed表示您已将None分配给不应为None的字段。
我不明白为什么在add_title()中这样做，因为您应该返回一个字符串，而不是Book对象（后来您将其分配为title以创建Book）。
模型中的pages = models.PositiveSmallIntegerField()字段没有default或null参数。
您应该添加默认值
pages = models.PositiveSmallIntegerField(default=123)
或允许它为空
pages = models.PositiveSmallIntegerField(null=True)
不要忘记更改模型后执行迁移！
而且，在创建伪数据时，您似乎没有在字段中输入任何值。