ImportError：无法导入名称和无法导入类

Question

I got a full code from github and everything was OK, server worked without any problems. But then I tried to do some changes, like adding a new class in the model.py and trying to import it to the admin.py I got such an error:

ImportError: cannot import name TechnicalExamination.

Of course, I did migrations before this, using python manage.py makemigrations and python manage.py migrate .

Here is my class in models.py:

class HealthExamination(models.Model):
class Meta:
    verbose_name_plural = 'Health Examinations'

doctor = models.CharField(max_length=70)
person = models.ForeignKey(Person, on_delete=models.CASCADE)
start_date = models.DateField()
end_date = models.DateField()

class TechnicalExamination(models.Model):
  class Meta:
    verbose_name_plural = 'Technical Examinations'

  technician = models.CharField(max_length=70)
  person = models.ForeignKey(Person, on_delete=models.CASCADE)
  start_date = models.DateField()
  end_date = models.DateField()

def get_fields(self):
    pairs = []
    for field in self._meta.fields:
        name = field.name
        try:
            pairs.append((name, getattr(self, "get_%s_display" % name)()))
        except AttributeError:
            pairs.append((name, getattr(self, name)))
    return pairs

def __str__(self):
  return str(self.person)

Here is my admin.py:

from __future__ import unicode_literals

from django.contrib import admin

from .models import Person, Car, InsuranceCompany, Policy,   HealthExamination, TechnicalExamination

admin.site.register(Person)
admin.site.register(Car)
admin.site.register(InsuranceCompany)
admin.site.register(Policy)
admin.site.register(HealthExamination)
admin.site.register(TechnicalExamination)

And here is my root:

Answer 1

1. Check migration file - you should have operations contain CreateModel your TechnicalExamination

    operations = [ migrations.CreateModel( name='TechnicalExamination', ... 

   If something wrong with migration files, remove migrations directory and makemigration again (You might need to clear your database , too) or use --fake

2. import from django shell:

    $python manage.py shell > from your_app_name.models import TechnicalExamination 

If not imported, you can see more detail error messages and debug it.

3. Try import by from destrict_office.models import TechnicalExamination

I experienced some problems with .models import method, and it's not clear import method.