Import and Export Data in Django

You can import and export data in your project’s database. Useful for:

creating a backup
transferring data to a different database, such as when switching to a different server or different database.
moving the project to a different computer
creating initial data for others who install your app

Export Data using dumpdata

The manage.py script has a dumpdata command to export part or all of your application database to a file. There are many useful options described in the django-admin dumpdata documentation.

You can specify which “apps” and which “tables” to dump
The data is in JSON format, which is human readable.

Create a dump of the “polls” models in JSON format. Output is to the console:

python manage.py dumpdata --indent=2 polls

The --indent=2 option requests output indented 2 spaces per nesting level. Ifyou don’t include ``–indent=xx` the output is very dense and hard to read.

There are 2 ways to output to a file:

# 1. redirect standard output to a file
python manage.py dumpdata --indent=2 polls > polls.json

# 2. use the -o option
python manage.py dumpdata --indent=2 -o polls.json polls 

Don’t forget the polls argument! If you omit it, then manage.py will dump all tables (including Django’s own tables) which is not portable.

Import Data Using loaddata

Import data into a database using:

python manage.py loaddata  polls.json

You can specify more than one data file. Sometimes the order matters. For example, if the “polls” data refers to “users” (a user owns his votes) then you might need to create users before loading polls data.

python manage.py loaddata users.json polls.json

If files are in a directory (e.g. data/, specify the path, too. For example

python manage.py loaddata data/users.json data/polls.json

Creating a “Data Fixture”

Django calls the initial data for an “app” a data fixture and it looks for this data in an “app” subdirectory named fixtures. For the polls app, the data fixture directory is polls/fixtures.

Suppose we want to create a start-up fixture named “seed”. The commands would be:

# create the fixtures directory (one time)
mkdir polls/fixtures
# export the polls data to seed.json
python manage.py dumpdata --indent=2 -o polls/fixtures/seed.json polls

Then edit polls/fixtures/seed.json to remove any unwanted data.

Loading a Data Fixture

If you specify a filename without a path, Django will look in the “fixtures” directories of all apps for the file.

To load the data into a fresh, empty database use:

python manage.py loaddata seed.json

See the django-admin docs for more dumpdata and loaddata options.

Using Data as Part of Installation

When someone installs your Django Polls project (or you deploy it to a cloud service) there won’t be a database.

So the installation process must run:

python manage.py migrate
python manage.py loaddata seed.json   (or whatever filename you choose)

Challenge for Hackers: Use a Migration instead of “manage.py loaddata”

You can create a migration file to load data into a database. This makes it easier for others to install your app, since they only need to run manage.py migrate.

There’s a good description and example in Data Migrations on RealPython.com.

Can you write a data migration (in Python) do read a JSON file created by dumpdata and load it into the database?

References

Providing Initial Data for Models describes how to create initial data using a Migration or a “fixture”. A “fixture” is a file containing data in JSON, XML, or Yaml format.

Data Migrations on RealPython.com describes how to create a data migration for initial data.

Other Ways to Import and Export Data

You can also use the database’s own import/export commands. These are specific to each database and the output format may differ slightly.

Django import-export add-on, with good documentation on ReadTheDocs.io. This add-on gives you finer control over import and export. The downside: adding another dependency to your project.