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Python Configuration Management

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Python configuration management via environment variables and typed settings. Use when externalizing config, setting up pydantic-settings, managing secrets, or implementing environment-specific behavior.

Originally by wshobson · MIT

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Python configuration management via environment variables and typed settings. Use when externalizing config, setting up pydantic-settings, managing secrets, or implementing environment-specific behavior.

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python-configuration/SKILL.md212 lines6.1 KBRawView on GitHub
Frontmatter — 2 properties
namepython-configuration
descriptionPython configuration management via environment variables and typed settings. Use when externalizing config, setting up pydantic-settings, managing secrets, or implementing environment-specific behavior.
1---
2name: python-configuration
3description: Python configuration management via environment variables and typed settings. Use when externalizing config, setting up pydantic-settings, managing secrets, or implementing environment-specific behavior.
4---A5 — No allowed-tools declared — no way to tell what this skill may touch
5 
6# Python Configuration Management
7 
8Externalize configuration from code using environment variables and typed settings. Well-managed configuration enables the same code to run in any environment without modification.
9 
10## When to Use This Skill
11 
12- Setting up a new project's configuration system
13- Migrating from hardcoded values to environment variables
14- Implementing pydantic-settings for typed configuration
15- Managing secrets and sensitive values
16- Creating environment-specific settings (dev/staging/prod)
17- Validating configuration at application startup
18 
19## Core Concepts
20 
21### 1. Externalized Configuration
22 
23All environment-specific values (URLs, secrets, feature flags) come from environment variables, not code.
24 
25### 2. Typed Settings
26 
27Parse and validate configuration into typed objects at startup, not scattered throughout code.
28 
29### 3. Fail Fast
30 
31Validate all required configuration at application boot. Missing config should crash immediately with a clear message.
32 
33### 4. Sensible Defaults
34 
35Provide reasonable defaults for local development while requiring explicit values for sensitive settings.
36 
37## Quick Start
38 
39```python
40from pydantic_settings import BaseSettings
41from pydantic import Field
42 
43class Settings(BaseSettings):
44 database_url: str = Field(alias="DATABASE_URL")
45 api_key: str = Field(alias="API_KEY")
46 debug: bool = Field(default=False, alias="DEBUG")
47 
48settings = Settings() # Loads from environment
49```
50 
51## Fundamental Patterns
52 
53### Pattern 1: Typed Settings with Pydantic
54 
55Create a central settings class that loads and validates all configuration.
56 
57```python
58from pydantic_settings import BaseSettings
59from pydantic import Field, PostgresDsn, ValidationError
60import sys
61 
62class Settings(BaseSettings):
63 """Application configuration loaded from environment variables."""
64 
65 # Database
66 db_host: str = Field(alias="DB_HOST")
67 db_port: int = Field(default=5432, alias="DB_PORT")
68 db_name: str = Field(alias="DB_NAME")
69 db_user: str = Field(alias="DB_USER")
70 db_password: str = Field(alias="DB_PASSWORD")
71 
72 # Redis
73 redis_url: str = Field(default="redis://localhost:6379", alias="REDIS_URL")
74 
75 # API Keys
76 api_secret_key: str = Field(alias="API_SECRET_KEY")
77 
78 # Feature flags
79 enable_new_feature: bool = Field(default=False, alias="ENABLE_NEW_FEATURE")
80 
81 model_config = {
82 "env_file": ".env",
83 "env_file_encoding": "utf-8",
84 }
85 
86# Create singleton instance at module load
87try:
88 settings = Settings()
89except ValidationError as e:
90 print(f"Configuration error:\n{e}")
91 sys.exit(1)
92```
93 
94Import `settings` throughout your application:
95 
96```python
97from myapp.config import settings
98 
99def get_database_connection():
100 return connect(
101 host=settings.db_host,
102 port=settings.db_port,
103 database=settings.db_name,
104 )
105```
106 
107### Pattern 2: Fail Fast on Missing Configuration
108 
109Required settings should crash the application immediately with a clear error.
110 
111```python
112from pydantic_settings import BaseSettings
113from pydantic import Field, ValidationError
114import sys
115 
116class Settings(BaseSettings):
117 # Required - no default means it must be set
118 api_key: str = Field(alias="API_KEY")
119 database_url: str = Field(alias="DATABASE_URL")
120 
121 # Optional with defaults
122 log_level: str = Field(default="INFO", alias="LOG_LEVEL")
123 
124try:
125 settings = Settings()
126except ValidationError as e:
127 print("=" * 60)
128 print("CONFIGURATION ERROR")
129 print("=" * 60)
130 for error in e.errors():
131 field = error["loc"][0]
132 print(f" - {field}: {error['msg']}")
133 print("\nPlease set the required environment variables.")
134 sys.exit(1)
135```
136 
137A clear error at startup is better than a cryptic `None` failure mid-request.
138 
139### Pattern 3: Local Development Defaults
140 
141Provide sensible defaults for local development while requiring explicit values for secrets.
142 
143```python
144class Settings(BaseSettings):
145 # Has local default, but prod will override
146 db_host: str = Field(default="localhost", alias="DB_HOST")
147 db_port: int = Field(default=5432, alias="DB_PORT")
148 
149 # Always required - no default for secrets
150 db_password: str = Field(alias="DB_PASSWORD")
151 api_secret_key: str = Field(alias="API_SECRET_KEY")
152 
153 # Development convenience
154 debug: bool = Field(default=False, alias="DEBUG")
155 
156 model_config = {"env_file": ".env"}
157```
158 
159Create a `.env` file for local development (never commit this):
160 
161```bash
162# .env (add to .gitignore)
163DB_PASSWORD=local_dev_password
164API_SECRET_KEY=dev-secret-key
165DEBUG=true
166```
167 
168### Pattern 4: Namespaced Environment Variables
169 
170Prefix related variables for clarity and easy debugging.
171 
172```bash
173# Database configuration
174DB_HOST=localhost
175DB_PORT=5432
176DB_NAME=myapp
177DB_USER=admin
178DB_PASSWORD=secret
179 
180# Redis configuration
181REDIS_URL=redis://localhost:6379
182REDIS_MAX_CONNECTIONS=10
183 
184# Authentication
185AUTH_SECRET_KEY=your-secret-key
186AUTH_TOKEN_EXPIRY_SECONDS=3600
187AUTH_ALGORITHM=HS256
188 
189# Feature flags
190FEATURE_NEW_CHECKOUT=true
191FEATURE_BETA_UI=false
192```
193 
194Makes `env | grep DB_` useful for debugging.
195 
196## Detailed worked examples and patterns
197 
198Detailed sections (starting with `## Advanced Patterns`) live in `references/details.md`. Read that file when the navigation summary above is insufficient.
199 
200## Best Practices Summary
201 
2021. **Never hardcode config** - All environment-specific values from env vars
2032. **Use typed settings** - Pydantic-settings with validation
2043. **Fail fast** - Crash on missing required config at startup
2054. **Provide dev defaults** - Make local development easy
2065. **Never commit secrets** - Use `.env` files (gitignored) or secret managers
2076. **Namespace variables** - `DB_HOST`, `REDIS_URL` for clarity
2087. **Import settings singleton** - Don't call `os.getenv()` throughout code
2098. **Document all variables** - README should list required env vars
2109. **Validate early** - Check config correctness at boot time
21110. **Use secrets_dir** - Support mounted secrets in containers
212 

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