ValueError: variable needs to have a value for field "id" before this many to many relationship can be used - Django
ValueError: variable needs to have a value for field "id" before this many to many relationship can be used - Django
我在 Django 中创建了一个数据模型,现在我创建了一个脚本来使用 web-scraped 值自动填充模型。但是,当我 运行 脚本时,出现以下错误:
ValueError: 变量需要有字段 "id" 的值才能使用这种多对多关系
Models.py
class Books(models.Model):
title = models.CharField(max_length=100)
def __str__(self):
return self.title
class Meta:
ordering = ['-title']
class Author(models.Model):
book = models.ManyToManyField(Books)
first_name = models.CharField(max_length=150)
last_name = models.CharField(max_length=200)
def __str__(self):
return "{} {}".format(self.first_name, self.last_name)
class Meta:
ordering = ['last_name','first_name']
class Book_details(models.Model):
book = models.ForeignKey(Books,
on_delete=models.CASCADE,
null=True) # models.SET_NULL weggehaald
pages = models.CharField(max_length=250)
publ_year = models.CharField(max_length=250)
edition = models.CharField(max_length=30) # paperback, hardcover, audiobook, etc
def __str__(self):
return "{} - pages: <{}>, edition: <{}>".format(self.book.title,
self.pages,
self.edition)#
class Cover(models.Model):
book = models.OneToOneField(Books,
on_delete=models.CASCADE)
path = models.CharField(max_length=500)
def __str__(self):
return "<Cover <path={}>".format(self.id, self.path)
populate_script
def add_book(title):
b = Books.objects.get_or_create(title = title)[0]
print(b)
b.save()
return b
def populate(scraped_tuple):
fake = Faker()
for _ in range(len(scraped_tuple)):
b_title = scraped_tuple[_][0][0]
new_book = add_book(b_title)
b_author_first = scraped_tuple[_][0][1].split(" ")[0]
b_author_last = scraped_tuple[_][0][1].split(" ")[1]
b_pages = scraped_tuple[_][0][2].split(" ")[0]
b_publ_year = fake.year()
b_edition = scraped_tuple[_][0][3].split(",")[0]
b_cover = scraped_tuple[_][0][4]
new_details = Book_details.objects.get_or_create(book = new_book, pages = b_pages, publ_year = b_publ_year, edition = b_edition)[0]
new_author = Author.objects.get_or_create(book = new_book, first_name = b_author_first, last_name = b_author_last)[0]
new_cover = Cover.objects.get_or_create(book = new_book, path = b_cover)[0]
scraped_tuple 是来自包含详细信息的网络抓取工具的 return 值。
(部分)回溯:
Books.models.DoesNotExist: Author matching query does not exist.
File "C:\path\to\LibraryApp\Library_WebA
pp\Library\populate.py", line 45, in populate
new_author = Author.objects.get_or_create(book = new_book, first_name = b_author_first, last_nam
e = b_author_last)[0]
其次是:
ValueError: "<Author: Mary McCarthy>" needs to have a value for field "id" before this many-to-many relationship can be used.
因此,由于 Author 模型中的 many-to-many 字段 "book",在尝试执行 new_author 语句时似乎出现了严重错误。我该如何解决这个问题。我是否需要像 add_book() 中的书籍那样为作者 object 提供类似的功能?
new_details 语句似乎执行得很好(标题和 book_details 正确显示在 Django 管理部分的数据库中)。
如 docs 中所述,用户 .add() 用于关联多对多字段中的记录。
def populate(scraped_tuple):
fake = Faker()
for _ in range(len(scraped_tuple)):
b_title = scraped_tuple[_][0][0]
new_book = add_book(b_title)
b_author_first = scraped_tuple[_][0][1].split(" ")[0]
b_author_last = scraped_tuple[_][0][1].split(" ")[1]
b_pages = scraped_tuple[_][0][2].split(" ")[0]
b_publ_year = fake.year()
b_edition = scraped_tuple[_][0][3].split(",")[0]
b_cover = scraped_tuple[_][0][4]
new_details = Book_details.objects.get_or_create(book = new_book, pages = b_pages, publ_year = b_publ_year, edition = b_edition)[0]
new_author = Author.objects.get_or_create(first_name = b_author_first, last_name = b_author_last)[0]
# add many to many fields this way:
new_author.book.add(new_book)
new_cover = Cover.objects.get_or_create(book = new_book, path = b_cover)[0]
我在 Django 中创建了一个数据模型,现在我创建了一个脚本来使用 web-scraped 值自动填充模型。但是,当我 运行 脚本时,出现以下错误: ValueError: 变量需要有字段 "id" 的值才能使用这种多对多关系
Models.py
class Books(models.Model):
title = models.CharField(max_length=100)
def __str__(self):
return self.title
class Meta:
ordering = ['-title']
class Author(models.Model):
book = models.ManyToManyField(Books)
first_name = models.CharField(max_length=150)
last_name = models.CharField(max_length=200)
def __str__(self):
return "{} {}".format(self.first_name, self.last_name)
class Meta:
ordering = ['last_name','first_name']
class Book_details(models.Model):
book = models.ForeignKey(Books,
on_delete=models.CASCADE,
null=True) # models.SET_NULL weggehaald
pages = models.CharField(max_length=250)
publ_year = models.CharField(max_length=250)
edition = models.CharField(max_length=30) # paperback, hardcover, audiobook, etc
def __str__(self):
return "{} - pages: <{}>, edition: <{}>".format(self.book.title,
self.pages,
self.edition)#
class Cover(models.Model):
book = models.OneToOneField(Books,
on_delete=models.CASCADE)
path = models.CharField(max_length=500)
def __str__(self):
return "<Cover <path={}>".format(self.id, self.path)
populate_script
def add_book(title):
b = Books.objects.get_or_create(title = title)[0]
print(b)
b.save()
return b
def populate(scraped_tuple):
fake = Faker()
for _ in range(len(scraped_tuple)):
b_title = scraped_tuple[_][0][0]
new_book = add_book(b_title)
b_author_first = scraped_tuple[_][0][1].split(" ")[0]
b_author_last = scraped_tuple[_][0][1].split(" ")[1]
b_pages = scraped_tuple[_][0][2].split(" ")[0]
b_publ_year = fake.year()
b_edition = scraped_tuple[_][0][3].split(",")[0]
b_cover = scraped_tuple[_][0][4]
new_details = Book_details.objects.get_or_create(book = new_book, pages = b_pages, publ_year = b_publ_year, edition = b_edition)[0]
new_author = Author.objects.get_or_create(book = new_book, first_name = b_author_first, last_name = b_author_last)[0]
new_cover = Cover.objects.get_or_create(book = new_book, path = b_cover)[0]
scraped_tuple 是来自包含详细信息的网络抓取工具的 return 值。
(部分)回溯:
Books.models.DoesNotExist: Author matching query does not exist.
File "C:\path\to\LibraryApp\Library_WebA
pp\Library\populate.py", line 45, in populate
new_author = Author.objects.get_or_create(book = new_book, first_name = b_author_first, last_nam
e = b_author_last)[0]
其次是:
ValueError: "<Author: Mary McCarthy>" needs to have a value for field "id" before this many-to-many relationship can be used.
因此,由于 Author 模型中的 many-to-many 字段 "book",在尝试执行 new_author 语句时似乎出现了严重错误。我该如何解决这个问题。我是否需要像 add_book() 中的书籍那样为作者 object 提供类似的功能? new_details 语句似乎执行得很好(标题和 book_details 正确显示在 Django 管理部分的数据库中)。
如 docs 中所述,用户 .add() 用于关联多对多字段中的记录。
def populate(scraped_tuple):
fake = Faker()
for _ in range(len(scraped_tuple)):
b_title = scraped_tuple[_][0][0]
new_book = add_book(b_title)
b_author_first = scraped_tuple[_][0][1].split(" ")[0]
b_author_last = scraped_tuple[_][0][1].split(" ")[1]
b_pages = scraped_tuple[_][0][2].split(" ")[0]
b_publ_year = fake.year()
b_edition = scraped_tuple[_][0][3].split(",")[0]
b_cover = scraped_tuple[_][0][4]
new_details = Book_details.objects.get_or_create(book = new_book, pages = b_pages, publ_year = b_publ_year, edition = b_edition)[0]
new_author = Author.objects.get_or_create(first_name = b_author_first, last_name = b_author_last)[0]
# add many to many fields this way:
new_author.book.add(new_book)
new_cover = Cover.objects.get_or_create(book = new_book, path = b_cover)[0]