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Connecting from Python | Tarantool
 
Connecting from Python
Connecting from Python

Connecting from Python

Connecting from Python

Pre-requisites

Before we proceed:

  1. Install the tarantool module. We recommend using python3 and pip3.

  2. Start Tarantool (locally or in Docker) and make sure that you have created and populated a database as we suggested earlier:

    box.cfg{listen = 3301}
    s = box.schema.space.create('tester')
    s:format({
             {name = 'id', type = 'unsigned'},
             {name = 'band_name', type = 'string'},
             {name = 'year', type = 'unsigned'}
             })
    s:create_index('primary', {
             type = 'hash',
             parts = {'id'}
             })
    s:create_index('secondary', {
             type = 'hash',
             parts = {'band_name'}
             })
    s:insert{1, 'Roxette', 1986}
    s:insert{2, 'Scorpions', 2015}
    s:insert{3, 'Ace of Base', 1993}
    

    Important

    Please do not close the terminal window where Tarantool is running – you’ll need it soon.

  3. In order to connect to Tarantool as an administrator, reset the password for the admin user:

    box.schema.user.passwd('pass')
    

Connecting to Tarantool

To get connected to the Tarantool server, say this:

>>> import tarantool
>>> connection = tarantool.connect("localhost", 3301)

You can also specify the user name and password, if needed:

>>> tarantool.connect("localhost", 3301, user=username, password=password)

The default user is guest.

Manipulating the data

A space is a container for tuples. To access a space as a named object, use connection.space:

>>> tester = connection.space('tester')

Inserting data

To insert a tuple into a space, use insert:

>>> tester.insert((4, 'ABBA', 1972))
[4, 'ABBA', 1972]

Querying data

Let’s start with selecting a tuple by the primary key (in our example, this is the index named primary, based on the id field of each tuple). Use select:

>>> tester.select(4)
[4, 'ABBA', 1972]

Next, select tuples by a secondary key. For this purpose, you need to specify the number or name of the index.

First off, select tuples using the index number:

>>> tester.select('Scorpions', index=1)
[2, 'Scorpions', 2015]

(We say index=1 because index numbers in Tarantool start with 0, and we’re using our second index here.)

Now make a similar query by the index name and make sure that the result is the same:

>>> tester.select('Scorpions', index='secondary')
[2, 'Scorpions', 2015]

Finally, select all the tuples in a space via a select with no arguments:

>>> tester.select()

Updating data

Update a field value using update:

>>> tester.update(4, [('=', 1, 'New group'), ('+', 2, 2)])

This updates the value of field 1 and increases the value of field 2 in the tuple with id = 4. If a tuple with this id doesn’t exist, Tarantool will return an error.

Now use replace to totally replace the tuple that matches the primary key. If a tuple with this primary key doesn’t exist, Tarantool will do nothing.

>>> tester.replace((4, 'New band', 2015))

You can also update the data using upsert that works similarly to update, but creates a new tuple if the old one was not found.

>>> tester.upsert((4, 'Another band', 2000), [('+', 2, 5)])

This increases by 5 the value of field 2 in the tuple with id = 4, – or inserts the tuple (4, "Another band", 2000) if a tuple with this id doesn’t exist.

Deleting data

To delete a tuple, use delete(primary_key):

>>> tester.delete(4)
[4, 'New group', 2012]

To delete all tuples in a space (or to delete an entire space), use call. We’ll focus on this function in more detail in the next section.

To delete all tuples in a space, call space:truncate:

>>> connection.call('box.space.tester:truncate', ())

To delete an entire space, call space:drop. This requires connecting to Tarantool as the admin user:

>>> connection.call('box.space.tester:drop', ())

Executing stored procedures

Switch to the terminal window where Tarantool is running.

Note

If you don’t have a terminal window with remote connection to Tarantool, check out these guides:

Define a simple Lua function:

function sum(a, b)
    return a + b
end

Now we have a Lua function defined in Tarantool. To invoke this function from python, use call:

>>> connection.call('sum', (3, 2))
5

To send bare Lua code for execution, use eval:

>>> connection.eval('return 4 + 5')
9