django第三方类库 - django-south 项目开始中就使用south方法

提炼 http://south.readthedocs.org/en/latest/tutorial/part1.html 官方手册里面的步骤

在新项目中使用

第一步创建项目

django-admin.py startproject LearnSouth

创建app

django-admin.py startapp books

在learnSouth.settings中修改数据库

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.
        'NAME': 'demo.db',                      # Or path to database file if using sqlite3.
        # The following settings are not used with sqlite3:
        'USER': '',
        'PASSWORD': '',
        'HOST': '',                      # Empty for localhost through domain sockets or '127.0.0.1' for localhost through TCP.
        'PORT': '',                      # Set to empty string for default.
    }
}

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # Uncomment the next line to enable the admin:
    # 'django.contrib.admin',
    # Uncomment the next line to enable admin documentation:
    # 'django.contrib.admindocs',
    'south',
    'LearnSouth',
    'books',
)

命令行执行导入数据库

./manage.py syncdb

初始化迁移信息

./manage.py schemamigration book --initial

执行完以后会在books目录下看到1个migrations文件夹。里面保存了

0001_initial.py 打开看一下。暂时里面没有数据

修改models.py文件内容

from django.db import models

# Create your models here.

class XiaoShuo(models.Model):
    create_date = models.DateTimeField(auto_created=True)
    public_date = models.DateTimeField(auto_now=True)
    title = models.CharField(max_length=128)
    contnet = models.CharField(max_length=512000)

class Comment(models.Model):
    username = models.CharField(max_length=64)
    email = models.CharField(max_length=64)
    # email = models.EmailField()

执行

./manage.py schemamigration books --auto

查看migrations目录。发现生成

0002_auto_add_xiaoshuo_add_comment.py文件。代码为

class Migration(SchemaMigration):

    def forwards(self, orm):
        # Adding model 'XiaoShuo'
        db.create_table(u'books_xiaoshuo', (
            (u'id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
            ('create_date', self.gf('django.db.models.fields.DateTimeField')()),
            ('public_date', self.gf('django.db.models.fields.DateTimeField')(auto_now=True, blank=True)),
            ('title', self.gf('django.db.models.fields.CharField')(max_length=128)),
            ('contnet', self.gf('django.db.models.fields.CharField')(max_length=512000)),
        ))
        db.send_create_signal(u'books', ['XiaoShuo'])

        # Adding model 'Comment'
        db.create_table(u'books_comment', (
            (u'id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
            ('username', self.gf('django.db.models.fields.CharField')(max_length=64)),
            ('email', self.gf('django.db.models.fields.CharField')(max_length=64)),
        ))
        db.send_create_signal(u'books', ['Comment'])


    def backwards(self, orm):
        # Deleting model 'XiaoShuo'
        db.delete_table(u'books_xiaoshuo')

        # Deleting model 'Comment'
        db.delete_table(u'books_comment')


    models = {
        u'books.comment': {
            'Meta': {'object_name': 'Comment'},
            'email': ('django.db.models.fields.CharField', [], {'max_length': '64'}),
            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
            'username': ('django.db.models.fields.CharField', [], {'max_length': '64'})
        },
        u'books.xiaoshuo': {
            'Meta': {'object_name': 'XiaoShuo'},
            'contnet': ('django.db.models.fields.CharField', [], {'max_length': '512000'}),
            'create_date': ('django.db.models.fields.DateTimeField', [], {}),
            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
            'public_date': ('django.db.models.fields.DateTimeField', [], {'auto_now': 'True', 'blank': 'True'}),
            'title': ('django.db.models.fields.CharField', [], {'max_length': '128'})
        }
    }

    complete_apps = ['books']

修改models.py代码为

class XiaoShuo(models.Model):
    create_date = models.DateTimeField(auto_created=True)
    public_date = models.DateTimeField(auto_now=True)
    title = models.CharField(max_length=128)
    contnet = models.CharField(max_length=512000)

class Comment(models.Model):
    username = models.CharField(max_length=64)
    email = models.CharField(max_length=64)
    # email = models.EmailField()

生成0003_auto_chg_field_comment_email.py

import datetime
from south.db import db
from south.v2 import SchemaMigration
from django.db import models


class Migration(SchemaMigration):

    def forwards(self, orm):

        # Changing field 'Comment.email'
        db.alter_column(u'books_comment', 'email', self.gf('django.db.models.fields.EmailField')(max_length=75))

    def backwards(self, orm):

        # Changing field 'Comment.email'
        db.alter_column(u'books_comment', 'email', self.gf('django.db.models.fields.CharField')(max_length=64))

    models = {
        u'books.comment': {
            'Meta': {'object_name': 'Comment'},
            'email': ('django.db.models.fields.EmailField', [], {'max_length': '75'}),
            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
            'username': ('django.db.models.fields.CharField', [], {'max_length': '64'})
        },
        u'books.xiaoshuo': {
            'Meta': {'object_name': 'XiaoShuo'},
            'contnet': ('django.db.models.fields.CharField', [], {'max_length': '512000'}),
            'create_date': ('django.db.models.fields.DateTimeField', [], {}),
            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
            'public_date': ('django.db.models.fields.DateTimeField', [], {'auto_now': 'True', 'blank': 'True'}),
            'title': ('django.db.models.fields.CharField', [], {'max_length': '128'})
        }
    }

    complete_apps = ['books']

执行

./manage.py migrate books

把修改后的模型合并到字段。

在老项目中使用

首先把south添加到install_apps变量中。

然后执行

./manage.py syncdb

之后执行转换,south会假装执行合并过程

./manage.py convert_to_south myapp

项目拷贝到其他机器上使用的过程中。如果修改提交。必须要执行

./manage.py migrate myapp 0001 --fake

如果没有数据库的项目，则不需要以上步骤。只需要执行syncdb同步到db。

数据迁移

在实践项目中，对模型的的修改往往伴随数据的修改。

比如原有的用户表采用了明文密码。在新版本中需要修改为加密的密码。通常开发过程中需要后台和db的配合。

后台修改字段，db部分在修改。

这里south的强大之处就出来了。可以在代码中修改迁移数据。

注意：一定要备份数据库

下面说说使用demo

首先建立1个app

./manager.py startapp book2

之后在模型里面添加数据

from django.db import models

class User(models.Model):

    username = models.CharField(max_length=255)
    password = models.CharField(max_length=60)
    name = models.TextField()

初始化数据记录

./manage.py schemamigration --initial book2

合并到数据库

./manage.py migrate book2

添加数据

./manage.py shell

User.objects.create(username="andrew", password="ihopetheycantseethis", name="Andrew Godwin")

以上步骤模拟了在实际过程中第一版的开发和数据导入。

接下来更新版本。密码修改为加密部分。

首先修改模型

from django.db import models

# Create your models here.

import hashlib

class User(models.Model):

    username = models.CharField(max_length=255)
    # password = models.CharField(max_length=60)
    password_salt = models.CharField(max_length=8, null=True)
    password_hash = models.CharField(max_length=40, null=True)
    name = models.TextField()

    def check_password(self, password):
        return hashlib.sha1(self.password_salt + password).hexdigest() == self.password_hash

执行合并数据库

./manage.py schemamigration book2 --auto

下面是好玩的部分。新建1个数据迁移记录

./manage.py datamigration book2 hash_passwords

在 migrations文件夹下面生成1份0003_hash_password.py文件。

修改forwards函数。

def forwards(self, orm):
        "Write your forwards methods here."
        # Note: Don't use "from appname.models import ModelName". 
        # Use orm.ModelName to refer to models in this application,
        # and orm['appname.ModelName'] for models in other applications.
        import random, hashlib, string
        for user in orm.User.objects.all():
            user.password_salt = "".join([random.choice(string.letters) for i in range(8)])
            user.password_hash = hashlib.sha1(user.password_salt + user.password).hexdigest()
            user.save()

forwards函数里面。执行了修改密码，导入部分。

回退函数也修改

def backwards(self, orm):
        "Write your backwards methods here."
        raise RuntimeError("cannot reverse this migration.")

接下来删除models.py中原始的password字段。

执行合并

outekiMacBook-Air:LearnSouth watsy$ ./manage.py schemamigration book2 --auto
/Users/watsy/Documents/code/gitoschina/python/LearnSouth/book2/models.py:7: DeprecationWarning: the sha module is deprecated; use the hashlib module instead
  import sha

 ? The field 'User.password' does not have a default specified, yet is NOT NULL.
 ? Since you are removing this field, you MUST specify a default
 ? value to use for existing rows. Would you like to:
 ?  1. Quit now, and add a default to the field in models.py
 ?  2. Specify a one-off value to use for existing columns now
 ?  3. Disable the backwards migration by raising an exception.
 ? Please select a choice: 2
 ? Please enter Python code for your one-off default value.
 ? The datetime module is available, so you can do e.g. datetime.date.today()
 >>> ""
 - Deleted field password on book2.User
Created 0004_auto__del_field_user_password.py. You can now apply this migration with: ./manage.py migrate book2

执行合并到数据库

outekiMacBook-Air:LearnSouth watsy$ ./manage.py migrate book2
/Users/watsy/Documents/code/gitoschina/python/LearnSouth/book2/models.py:7: DeprecationWarning: the sha module is deprecated; use the hashlib module instead
  import sha

Running migrations for book2:
 - Migrating forwards to 0004_auto__del_field_user_password.
 > book2:0002_auto__add_field_user_password_salt__add_field_user_password_hash
 > book2:0003_hash_passwords
 - Migration 'book2:0003_hash_passwords' is marked for no-dry-run.
 > book2:0004_auto__del_field_user_password
 - Loading initial data for book2.
Installed 0 object(s) from 0 fixture(s)

测试执行以后的数据库是否修改密码成功

outekiMacBook-Air:LearnSouth watsy$ ./manage.py shell

>>> from book2.models import User
>>> User.objects.get(id=1).check_password("258841679")
True
>>> User.objects.get(id=1).check_password("fakepass")
False

测试修改成功～