python-django-问题

 

django2.2版本

问题1：django.db.utils.OperationalError: (2006, 'MySQL server has gone away')

参考博文：https://www.cnblogs.com/ExMan/p/10171049.html

>>> from django.db import connection
>>> connection.close()
>>> import time
>>> time.sleep(10)
>>> User.objects.exists()
True
>>> User.objects.all()[:10]
<QuerySet [<User: weizitianming>, <User: weizitianming_0>, <User: weizitianming_1>, <User: weizitianming_2>, <User: weizitianming_3>, <User: weizitianming_4>, <User: weizitianming_5>, <User: weizitianming_6>, <User: weizitianmi
ng_7>, <User: weizitianming_8>]>
>>> 

问题解决。

 问题2，TypeError: __init__() missing 1 required positional argument: 'on_delete'  

解决：添加 on_delete=models.CASCADE

参考链接：https://www.cnblogs.com/phyger/p/8035253.html

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=50)

class Group(models.Model):
    name = models.CharField(max_length=128)
    members = models.ManyToManyField(
        Person,
        through='Membership',
        through_fields=('group', 'person'),
    )

class Membership(models.Model):
    group = models.ForeignKey(Group, on_delete=models.CASCADE)
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    inviter = models.ForeignKey(
        Person,
        on_delete=models.CASCADE,
        related_name="membership_invites",
    )
    invite_reason = models.CharField(max_length=64)

问题3： mysqlclient 安装报错：OSError: mysql_config not found 

#yum install mysql-devel gcc gcc-devel python-devel