![\"example](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/01-What-Are-Environment-Variables.jpg\")
<\/figure>\n\n\n\nEnvironment variables are dynamic named values that can affect how running processes behave on a computer. Some key properties of environment variables are:<\/p>\n\n\n\n
- \n
- Named<\/strong>: Have descriptive variable names like APP_MODE<\/em> and DB_URL<\/em>.<\/li>\n\n\n\n
- External<\/strong>: Values are set outside the app code via files, command lines, and systems.<\/li>\n\n\n\n
- Dynamic<\/strong>: Can update variables without restarting apps.<\/li>\n\n\n\n
- Configured<\/strong>: Code relies on variables but doesn\u2019t define them.<\/li>\n\n\n\n
- Decoupled<\/strong>: No need to alter code configurations once variables are set.<\/li>\n\n\n<\/ul>\n\n\n\n
Here’s an analogy<\/strong>. Imagine you’re following a chocolate chip cookie recipe. The recipe might say:<\/p>\n\n\n\n
- \n
- Add 1 cup of sugar<\/li>\n\n\n\n
- Add 1 stick of softened butter<\/li>\n\n\n\n
- Add 2 eggs<\/li>\n\n\n<\/ul>\n\n\n\n
Instead of those hard-coded values, you could use environment variables instead:<\/p>\n\n\n\n
- \n
- Add $SUGAR cup of sugar<\/li>\n\n\n\n
- Add $BUTTER sticks of softened butter<\/li>\n\n\n\n
- Add $EGGS eggs<\/li>\n\n\n<\/ul>\n\n\n\n
Before making the cookies, you’d set those environment variable names to values of your choosing:<\/p>\n\n\n\n
SUGAR=1 \nBUTTER=1\nEGGS=2<\/code><\/pre>\n\n\n\nSo, when following the recipe, your ingredients would resolve to:<\/p>\n\n\n\n
- \n
- Add 1 cup of sugar<\/li>\n\n\n\n
- Add 1 stick of softened butter<\/li>\n\n\n\n
- Add 2 eggs<\/li>\n\n\n<\/ul>\n\n\n\n
This allows you to configure the cookie recipe without changing the recipe code.<\/p>\n\n\n\n
The same concept applies to computing and development. Environment variables allow you to alter the environment in which a process runs without changing the underlying code. Here are a few common examples:<\/p>\n\n\n\n
- \n
- Setting the environment to “development” or “production”<\/li>\n\n\n\n
- Configuring API keys for external services<\/li>\n\n\n\n
- Passing in secret keys or credentials<\/li>\n\n\n\n
- Toggling certain features on and off<\/li>\n\n\n<\/ul>\n\n\n\n
Environment variables provide great flexibility. You can deploy the same code to multiple environments without changing the code itself. But let\u2019s understand further why they are valuable.<\/p>\n\n\n\n
Why Are Environment Variables Valuable?<\/h2>\n\n\n\n
![\"environment](\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\")
<\/figure>\n\n\n\nConsider environment variables like application knobs used to dial-in preferences. We will explore excellent use cases shortly.<\/p>\n\n\n\n
Let\u2019s solidify intuition on why environment variables matter!<\/p>\n\n\n\n
Reason #1: They Separate Application Code From Configurations<\/h3>\n\n\n\n
<\/figure>\n\n\n\nHard-coding configurations and credentials directly into your code can cause all sorts of problems:<\/p>\n\n\n\n
- \n
- Accidental commits to source control<\/li>\n\n\n\n
- Rebuilding and redeploying code just to change a value<\/li>\n\n\n\n
- Configuration issues when promoting across environments<\/li>\n\n\n<\/ul>\n\n\n\n
It also leads to messy code:<\/p>\n\n\n\n
import os\n\n# Hard-coded configuration\nDB_USER = 'appuser' \nDB_PASS = 'password123'\nDB_HOST = 'localhost'\nDB_NAME = 'myappdb'\n\ndef connect_to_db():\n print(f\"Connecting to {DB_USER}:{DB_PASS}@{DB_HOST}\/{DB_NAME}\") \n\nconnect_to_db()<\/code><\/pre>\n\n\n\nThis entangles business logic with configuration details. Tight coupling makes maintenance arduous over time:<\/p>\n\n\n\n
- \n
- Changes require modifying the source code<\/li>\n\n\n\n
- Risk of leaking secrets into source control<\/li>\n\n\n<\/ul>\n\n\n\n
Using environment variables reduces these issues. For instance, you can set the DB_USER and DB_NAME environment variables.<\/p>\n\n\n\n
# .env file\nDB_USER=appuser\nDB_PASS=password123 \nDB_HOST=localhost\nDB_NAME=myappdb<\/code><\/pre>\n\n\n\nThe application code can access the environment variables whenever required, keeping the code clean and simple.<\/p>\n\n\n\n
import os\n\n# Load config from environment \nDB_USER = os.environ['DB_USER']\nDB_PASS = os.environ['DB_PASS'] \nDB_HOST = os.environ['DB_HOST']\nDB_NAME = os.environ['DB_NAME']\n\ndef connect_to_db():\n print(f\"Connecting to {DB_USER}:{DB_PASS}@{DB_HOST}\/{DB_NAME}\")\n \nconnect_to_db()<\/code><\/pre>\n\n\n\nEnvironment variables cleanly separate configuration from code, keeping sensitive values abstracted into the environment.<\/p>\n\n\n\n
You can deploy the same code from development to production without changing a thing. The environment variables can differ between environments without impacting the code at all.<\/p>\n\n\n\n
Reason #2: They Simplify Configuring Applications<\/h3>\n\n\n\n
<\/figure>\n\n\n\nEnvironment variables simplify tweaking configurations without touching code:<\/p>\n\n\n\n
# .env file:\nDEBUG=true<\/code><\/pre>\n\n\n\nHere\u2019s how we could use it within the script file:<\/p>\n\n\n\n
# Script content:\nimport os\n\nDEBUG = os.environ.get('DEBUG') == 'true' \n\nif DEBUG:\n print(\"In DEBUG mode\")<\/code><\/pre>\n\n\n\nToggling debug mode requires only updating the .env file\u2014no code changes, rebuilding, or redeploying are needed. \u201cEnv vars\u201d for short, also help deploy across environments seamlessly:<\/p>\n\n\n\n
import os\n\n# Retrieve environment variable to determine the current environment (production or staging)\ncurrent_env = os.getenv('APP_ENV', 'staging') # Default to 'staging' if not set\n\n# Production API key\nPROD_API_KEY = os.environ['PROD_API_KEY']\n\n# Staging API key\nSTG_API_KEY = os.environ['STG_API_KEY']\n\n# Logic that sets api_key based on the current environment\nif current_env == 'production':\n api_key = PROD_API_KEY\nelse:\n api_key = STG_API_KEY\n\n# Initialize API client with the appropriate API key\napi = ApiClient(api_key)<\/code><\/pre>\n\n\n\nThe same code can use separate API<\/a> keys for production vs staging without any changes.<\/p>\n\n\n\n
And lastly, they enable feature toggles without new deployments:<\/p>\n\n\n\n
NEW_FEATURE = os.environ['NEW_FEATURE'] == 'true'\n\nif NEW_FEATURE:\n enableNewFeature()<\/code><\/pre>\n\n\n\nChanging the NEW_FEATURE<\/em> var activates functionality instantly within our code. The interface for updating configurations depends on the systems:<\/p>\n\n\n\n
- \n
- Cloud<\/a> platforms like Heroku use web dashboards<\/li>\n\n\n\n
- Servers use OS command tools<\/li>\n\n\n\n
- Local dev can use .env files<\/li>\n\n\n<\/ul>\n\n\n\n
Environment variables are beneficial when creating applications, allowing users to configure elements per their requirements.<\/p>\n\n\n\n
Reason #3: They Help Manage Secrets And Credentials<\/h3>\n\n\n\n
<\/figure>\n\n\n\nChecking secrets like API keys, passwords, and private keys directly into source code raises substantial security risks<\/a>:<\/p>\n\n\n\n
# Avoid exposing secrets in code!\nSTRIPE_KEY = 'sk_live_1234abc'\nDB_PASSWORD = 'password123'\n\nstripe.api_key = STRIPE_KEY \ndb.connect(DB_PASSWORD)<\/code><\/pre>\n\n\n\n
- Cloud<\/a> platforms like Heroku use web dashboards<\/li>\n\n\n\n
- External<\/strong>: Values are set outside the app code via files, command lines, and systems.<\/li>\n\n\n\n
![\"environment](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/02-Why-Are-Environment-Variables-Valuable.jpg\")
<\/figure>\n\n\n\n![\"reason](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/03-They-Separate-Application-Code-From-Configurations.jpg\")
<\/figure>\n\n\n\n![\"Application](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/04-They-Simplify-Configuring-Applications.jpg\")
<\/figure>\n\n\n\n![\"application](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/05-They-Help-Manage-Secrets-And-Credentials.jpg\")
<\/figure>\n\n\n\n![\"configuration](\"https:\/\/www.dreamhost.com\/blog\/wp-content\/uploads\/2024\/03\/06-They-Promote-Consistency.jpg\")
<\/figure>\n\n\n\n