Getting Started

Requirements: Python 3

Create a Thing

To interact with Bucket, the first step is to visit Bucket to create an account and a Thing.

During this process you will get the ID of your Thing (starting with dcd:things:…) and you will generate a public/private key.

These 2 pieces of information are needed for your Python code to interact with Bucket.

Setup a Python project

Create a folder for your project and open it with VisualStudio Code.

To avoid disturbing other Python setup on your machine, we setup a virtual environment with virtualenv. To create a virtual environment called venv, open the terminal (VisualStudio Code, directly in your project) and execute the following command:

virtualenv venv

Then we activate this environment with source:

source venv/bin/activate

If it worked properly, you should see (venv) appearing on the left side of the line in the Terminal.

We can now install the DCD SDK library

pip install dcd-sdk

At this stage you can be prompted to update your pip module, you can do so with:

pip install --upgrade pip

Your Python setup is now ready.

Basic example

In this example, we will create a property Accelerometer generating random values. It shows how to establish a connection with Bucket using your Thing id and your private key. This is a typical case for a Python code running on a device to collect data.

In the file explorer (left-side panel), create a new file example.py and add the following lines.

 # Import Thing from the Data-Centric Design
 from dcd.bucket.thing import Thing

 # Create an instance of Thing
 # (Replace with your thing id and the path to your private key)
 my_thing = Thing(thing_id="dcd:things:7f7fe4c6-45e9-42d2-86e2-a6794e386108",
                 private_key_path="/path/to/private.pem")

You can run this example in the terminal:

python example.py

To stop the program, press CTRL+C.

Once the connection is established with your Thing, we can get an overview of this Thing by printing the output of the method to_json(). Add the following line at the bottom of the file and run the program again. If you just registered your Thing on Bucket, it has only an id, a name and a type.

print(my_thing.describe())

Let’s create a property ‘My Python accelerometer’. The method find_or_create() looks for an existing property with this name. If none is found, it creates a new on with the type ‘ACCELEROMETER’

my_property = my_thing.find_or_create_property(
    "My Python Accelerometer", "ACCELEROMETER")

Let’s have a look at the property, it should contain the name and a unique id. The type also contains the dimensions, 3 in the case of an accelerometer.

print(my_property.describe())

We are ready to send data. In the code below we create a function that generates an array with 3 random values and add them to the property. We then make an infinite loop (while True) to send these random values every 2 seconds.

To generate random numbers we need the library random and to wait 2 seconds we need the library time. These are part of Python, we just import them at the top of the file.

from random import random
import time

Then, we can write our function at the bottom of the file.

 # Let's create a function that generate random values
 def generate_dum_property_values(the_property):
     # Define a tuple with the current time, and 3 random values
     values = (random(), random(), random())
     # Update the values of the property
     the_property.update_values(values)

 # Finally, we call our function to start generating dum values
 while True:
     generate_dum_property_values(my_property)
     # Have a 2-second break
     time.sleep(2)

Environment Variables

To avoid credentials in your code, the DCD Python Kit is looking for your thing id and private key from the environment variables. To set these variables, create a file .env and add the following lines (replace the thing id and the path by yours).

THING_ID=dcd:things:7f7fe4c6-45e9-42d2-86e2-a6794e386108
PRIVATE_KEY_PATH=/path/to/private.pem

The full example can be found Here