Django ValueError: Cannot assign必须是实例

Question

当我试图通过manage.py shell向数据库插入数据时，我得到了这个错误

ValueError: Cannot assign "'Ciawigebang'": "Desa.kecamatan" must be a "Kecamatan" instance.

this is my models.py

from django.db import models
class Kecamatan(models.Model):
kecamatan = models.CharField(max_length=30)
def __str__(self):
return self.kecamatan
class Desa(models.Model):
desa = models.CharField(max_length=30)
kecamatan = models.ForeignKey(Kecamatan, null=True, blank=True, on_delete=models.CASCADE)
def __str__(self):
return self.desa

这里是我的json文件片段scrap.json

[
{
"Kecamatan": "Ciawigebang",
"Desa": [
"Ciawigebang",
"Ciawilor",
"Cigarukgak",
"Cihaur",
"Cihirup",
"Cijagamulya",
"Cikubangmulya",
"Ciomas",
"Ciputat",
"Dukuhdalem",
"Geresik",
"Kadurama",
"Kapandayan",
"Karangkamulya",
"Kramatmulya",
"Lebaksiuh",
"Mekarjaya",
"Padarama",
"Pajawanlor",
"Pamijahan",
"Pangkalan",
"Sidaraja",
"Sukadana",
"Sukaraja"
]
},{
"Kecamatan": "Cibeureum",
"Desa": [
"Cibeureum",
"Cimara",
"Kawungsari",
"Randusari",
"Sukadana",
"Sukarapih",
"Sumurwiru",
"Tarikolot"
]
},{
"Kecamatan": "Cibingbin",
"Desa": [
"BANTAR PANJANG",
"CIANGIR",
"Cibingbin",
"Cipondok",
"CISAAT",
"Citenjo",
"DUKUHBADAG",
"Sindang Jawa",
"SUKA MAJU",
"SUKAHARJA"
]
}...
]

这是我用来从python management .py shell

插入数据到数据库的代码

import json
from apps.models import Desa, Kecamatan
with open('scrap.json') as f:
daerahs = json.load(f)
for daerah in daerahs:
for x in daerah['Desa']:
y=Desa(desa=x, kecamatan=daerah['Kecamatan'])
y.save()

如何解决?有很多类似的问题，但我不知道如何解决这个问题。谢谢你的帮助……

Answer 1

需要创建一个Kecamatan instance。将代码更改为

for daerah in daerahs:
kecamatan, created = Kecamatan.objects.get_or_create(kecamatan=daerah['Kecamatan'])
for x in daerah['Desa']:
y = Desa(desa=x, kecamatan=kecamatan)
y.save()

点击此链接了解get_or_create

Answer 2

您需要从您的终端python manage.py loaddata scrap.json使用loaddata

加载数据的格式应该像这样:

[
{
"pk": 1,
"model": "app.desa",
"fields": {
"kecamatan": 1,
"desa": "Ciawigebang"
},
{
"pk": 2,
"model": "app.desa",
"fields": {
"kecamatan": 1,
"desa": "Ciawigebang"
}
]

对于Desa的每个实例，您提供一个唯一的id，对于字段kecamatan，您使用它的id，因为它是一个外键(在填充Desa模型之前，您需要用值填充Kecamatan模型)。

意味着你应该首先为Kecamatan创建另一个json文件，并加载loaddata

[
{
"pk": 1,
"model": "app.kecamatan",
"fields": {
"kecamatan": "Ciawigebang",
},
{
"pk": "Cibeureum",
"model": "app.kecamatan",
"fields": {
"kecamatan": 1,
}
]

注意:app应该是Desa和Kecamatan模型所在的应用的名称。