We've built a simple console application that demonstrates how LaunchDarkly's SDK works.

Below, you'll find the build procedure. For more comprehensive instructions, you can visit your Quickstart page or the Python reference guide.

This demo requires Python 3.9 or higher.

Before running the application, you need to set up a feature flag in your LaunchDarkly dashboard.

• Flag Type: Boolean flag
• Flag Key: sample-feature (default) or any custom key you set in LAUNCHDARKLY_FLAG_KEY
• Flag Name: You can name it anything descriptive like "Sample Feature" or "Demo Feature"

Since this is a boolean flag, you need two variations:

• Variation 1: true (Boolean)
• Variation 2: false (Boolean)

The program creates a specific user context that will appear in your LaunchDarkly dashboard:

• User Key: example-user-key
• User Kind: user
• User Name: Sandy

1. Go to your LaunchDarkly dashboard and navigate to your project

2. Create a new flag:

   • Click "Create Flag"
   • Choose "Boolean" as the flag type
   • Set the flag key to sample-feature (or your custom key)
   • Set the flag name to something like "Sample Feature"

3. Configure the flag variations:

   • Variation 1: true (Boolean)
   • Variation 2: false (Boolean)
   • Set the default variation to false

4. Set up targeting rules:

   • For the user "Sandy" (key: example-user-key):
     • Add a targeting rule that serves true to this specific user
   • For all other users:
     • Serve false (or whatever you want as the default)

5. Save and turn on the flag

Once you've created the flag, you can test it by running:

# Activate virtual environment
source venv/bin/activate

# Set your SDK key (replace with your actual key)
export LAUNCHDARKLY_SDK_KEY="your-actual-sdk-key-here"

# Optionally set a custom flag key (or leave it to use 'sample-feature')
export LAUNCHDARKLY_FLAG_KEY="sample-feature"

# Run the program
python main.py

• If the flag evaluates to true: You'll see the LaunchDarkly banner displayed
• If the flag evaluates to false: You'll see the evaluation result but no banner
• The program will wait for real-time changes: You can toggle the flag in LaunchDarkly and see the changes immediately

While the program is running:

1. Go to your LaunchDarkly dashboard
2. Find the flag you created
3. Toggle it between true and false
4. Watch the program output change in real-time

1. Create a .env file in the project root with your LaunchDarkly credentials:

   # Create .env file
   touch .env

2. Add your environment variables to the .env file:

   # LaunchDarkly Configuration
   LAUNCHDARKLY_SDK_KEY=your-sdk-key-here
   LAUNCHDARKLY_FLAG_KEY=sample-feature
   
   # Optional: Set to 'true' to run in CI mode (single evaluation)
   # CI=false

3. Install dependencies:

   # Using pip (recommended)
   python3 -m venv venv
   source venv/bin/activate
   pip install -r requirements.txt
   
   # Or using Poetry
   poetry install

4. Run the application:

   # Using pip
   source venv/bin/activate
   python main.py
   
   # Or using Poetry
   poetry run python main.py

1. Set the environment variable LAUNCHDARKLY_SDK_KEY to your LaunchDarkly SDK key. If there is an existing boolean feature flag in your LaunchDarkly project that you want to evaluate, set LAUNCHDARKLY_FLAG_KEY to the flag key; otherwise, a boolean flag of sample-feature will be assumed.

   export LAUNCHDARKLY_SDK_KEY="1234567890abcdef"
   export LAUNCHDARKLY_FLAG_KEY="my-boolean-flag"

2. Ensure you have Poetry installed.

3. Install the required dependencies with poetry install.

4. On the command line, run poetry run python main.py

You should receive the message "The feature flag evaluates to .". The application will run continuously and react to the flag changes in LaunchDarkly.

The .env file is included in .gitignore to prevent accidentally committing sensitive credentials to version control. Always keep your LaunchDarkly SDK keys secure and never commit them to public repositories.