57. Environment Variables

1. Introduction

Environment variables are dynamic values set outside Python. They are often used for configuration and secrets.

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2. Accessing Environment Variables

import os
print(os.getenv("HOME"))

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3. Setting Environment Variables

Linux/macOS:

export API_KEY=12345

Windows (cmd):

set API_KEY=12345

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4. Using in Python

api_key = os.getenv("API_KEY", "default_value")
print(api_key)

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5. Modifying in Python

os.environ["DEBUG"] = "true"
print(os.environ["DEBUG"])

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6. Best Practices

• Use env vars for secrets (API keys, passwords).
• Don’t hardcode sensitive values in code.
• Consider libraries like python-dotenv for .env files.

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7. Next Steps

✅ You now know environment variables.
Next: Introduction to Object-Oriented Programming (OOP).