Configuration files are used to store settings, preferences, and credentials for applications. Python provides multiple ways to read and write config files, making it easy to manage application settings.

---

1. Why Use Config Files?

✅ Separation of code and settings – No need to hardcode values in scripts.
✅ Easier maintenance – Modify settings without changing code.
✅ Environment-specific settings – Different configurations for development, testing, and production.
✅ Secure storage – Avoid storing sensitive information directly in scripts.

---

2. Config File Formats

Python supports various config file formats:
🔹 INI (configparser module) – Simple key-value pairs grouped into sections.
🔹 JSON (json module) – Lightweight and widely used for web applications.
🔹 YAML (pyyaml module) – Human-readable and supports complex structures.
🔹 TOML (toml module) – Used for Python project settings (pyproject.toml).
🔹 ENV Files (dotenv module) – Used for environment variables.

---

1. INI Configuration Files (configparser)

INI files contain sections with key-value pairs:

1.1 Sample config.ini File

[database]
host = localhost
port = 5432
username = admin
password = secret

[server]
debug = True
log_level = INFO

1.2 Reading INI Files

import configparser

config = configparser.ConfigParser()
config.read("config.ini")

# Access values
db_host = config["database"]["host"]
db_port = config.getint("database", "port")
debug_mode = config.getboolean("server", "debug")

print(f"Database Host: {db_host}")
print(f"Port: {db_port}")
print(f"Debug Mode: {debug_mode}")

1.3 Writing to an INI File

config["api"] = {"base_url": "https://api.example.com", "timeout": "30"}

with open("config.ini", "w") as configfile:
    config.write(configfile)

---

2. JSON Configuration Files (json Module)

JSON is a widely used format for configuration files in web and APIs.

2.1 Sample config.json File

{
    "database": {
        "host": "localhost",
        "port": 5432,
        "username": "admin",
        "password": "secret"
    },
    "server": {
        "debug": true,
        "log_level": "INFO"
    }
}

2.2 Reading JSON Files

import json

with open("config.json", "r") as file:
    config = json.load(file)

print(config["database"]["host"])  # Output: localhost
print(config["server"]["debug"])   # Output: True

2.3 Writing JSON Files

config["api"] = {"base_url": "https://api.example.com", "timeout": 30}

with open("config.json", "w") as file:
    json.dump(config, file, indent=4)

---

3. YAML Configuration Files (pyyaml Module)

YAML is human-friendly and supports nested structures.

3.1 Sample config.yaml File

database:
  host: localhost
  port: 5432
  username: admin
  password: secret

server:
  debug: true
  log_level: INFO

3.2 Reading YAML Files

import yaml

with open("config.yaml", "r") as file:
    config = yaml.safe_load(file)

print(config["database"]["host"])  # Output: localhost
print(config["server"]["debug"])   # Output: True

3.3 Writing YAML Files

config["api"] = {"base_url": "https://api.example.com", "timeout": 30}

with open("config.yaml", "w") as file:
    yaml.dump(config, file, default_flow_style=False)

Install pyyaml if not installed:

pip install pyyaml

---

4. TOML Configuration Files (toml Module)

TOML is commonly used for Python project settings.

4.1 Sample config.toml File

[database]
host = "localhost"
port = 5432
username = "admin"
password = "secret"

[server]
debug = true
log_level = "INFO"

4.2 Reading TOML Files

import toml

config = toml.load("config.toml")
print(config["database"]["host"])  # Output: localhost
print(config["server"]["debug"])   # Output: True

4.3 Writing TOML Files

config["api"] = {"base_url": "https://api.example.com", "timeout": 30}

with open("config.toml", "w") as file:
    toml.dump(config, file)

Install toml if not installed:

pip install toml

---

5. Environment Variables (dotenv Module)

ENV files store environment-specific settings.

5.1 Sample .env File

DATABASE_HOST=localhost
DATABASE_PORT=5432
DATABASE_USER=admin
DATABASE_PASS=secret

5.2 Reading .env Files

from dotenv import load_dotenv
import os

load_dotenv()  # Load environment variables from .env file

db_host = os.getenv("DATABASE_HOST")
db_port = os.getenv("DATABASE_PORT")

print(f"Database Host: {db_host}")
print(f"Port: {db_port}")

📌 Install python-dotenv if not installed:

pip install python-dotenv

---

6. Choosing the Right Format

Format	Best For	Pros	Cons
INI	Simple settings	Easy to read	Limited nesting
JSON	Web & API settings	Widely supported	No comments allowed
YAML	Complex configs	Human-friendly	Requires extra library
TOML	Python projects	Clear syntax	Less common
ENV	Environment settings	Easy to use	Flat structure