There was a problem testing Django today, and I was badly burned.

D:\pythonCode\django\mysite>django-admin.py startproject mysite

And then I’m going to create my APP, which I’m going to call MB

python manage.py startapp mb

The directory structure is as follows:

D:.
│  manage.py
│
├─mb
│      admin.py
│      models.py
│      models.pyc
│      tests.py
│      views.py
│      __init__.py
│      __init__.pyc
│
└─mysite
        settings.py
        settings.pyc
        urls.py
        wsgi.py
        __init__.py
        __init__.pyc

For testing, I created a very simple model
Modify the MB – & gt; Models.py, with only one field

from django.db import models

# Create your models here.
class Test(models.Model):
    testField = models.TextField()

 
Modify the mysite – & gt; settings.py

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'mysite.mb',
)

Note: This is where I want the database to be set to

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'D:\\test.db',
    }
}

 
 
When performing database tests

manage.py sql mb

Error message:

ImportError: No module named mb

Well, I set it in Settings.py, why don’t I have this model?
 
I don’t know, Baidu, will mysite-> Settings. Py

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'mb',
)

This time, there it is

BEGIN;
CREATE TABLE "mb_test" (
    "id" integer NOT NULL PRIMARY KEY,
    "testField" text NOT NULL
)
;

COMMIT;

 
It looks like a success, but why?For explanation.