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How to Load a .env File Manually in Python
Parse a .env-style key-value file into a Python dictionary using only the standard library, with comment and quoted-value handling.
import re
from pathlib import Path
def load_dotenv_file(filepath: str) -> dict[str, str]:
"""Parse a .env-style file into a dictionary."""
env = {}
path = Path(filepath)
if not path.exists():
raise FileNotFoundError(f"Environment file not found: {filepath}")
for line in path.read_text()…How to Read Environment Variables in Python with Default Values
Retrieve an environment variable safely using os.getenv() with a fallback default when the variable is missing.
import os
database_url = os.getenv("DATABASE_URL", "postgresql://localhost:5432/mydb")
print(f"Database URL: {database_url}")How to Debug Print Behind a DEBUG Environment Flag in Python
Create a debug_print function that only outputs when the DEBUG environment variable is set to a truthy value like 1, true, yes, or on.
import os
def debug_print(*args, **kwargs):
"""Print only when DEBUG environment variable is set to a truthy value."""
if os.environ.get("DEBUG", "").lower() in ("1", "true", "yes", "on"):
print(*args, **kwargs)
if __name__ == "__main__":
# Example usage: run as `DEBUG=1 python script.py` to se…How to Merge Environment-Specific Config JSON in Python
Loads a base JSON config and overlays environment-specific overrides, merging the two dictionaries into one final config.
import json
import pathlib
def load_config(base_path: pathlib.Path, env: str) -> dict:
base_config = json.loads(base_path.read_text())
env_path = base_path.with_name(f"config.{env}.json")
if env_path.exists():
env_config = json.loads(env_path.read_text())
return {**base_config, **env_conf…Parse Env Vars into Typed Dict in Python
Convert a list of environment variable names into a dictionary with automatically detected types (bool, int, float, or string), defaulting missing vars to None.
import os
from typing import Any, Dict
def parse_env_vars(env_names: list[str], env: Dict[str, str] | None = None) -> Dict[str, Any]:
"""Parse a list of environment variable names into a typed dict.
Each variable is parsed as:
- bool: "true"/"false" (case-insensitive)
- int: if it can be converted t…How to Build an Agent Loop with Plan, Act, Observe in Python
Implements a simple plan-act-observe loop that an AI agent uses to iteratively complete a task in an environment while storing observations in memory.
class Agent:
def __init__(self, name):
self.name = name
self.memory = {}
def plan(self, task):
return f"Plan for {task}: step 1, step 2, step 3"
def act(self, plan, environment):
return f"Executing {plan} in {environment}"
def observe(self, action_result):
sel…Create a Data Helper Class for Beginners in Python
A simple Python class to read and write JSON and CSV files from a local directory, ideal for automating data workflows in cloud environments.
import json
from pathlib import Path
class DataHelper:
"""Simple helper for reading and writing common data files."""
def __init__(self, directory="data"):
self.directory = Path(directory)
self.directory.mkdir(exist_ok=True)
def save_json(self, filename, data):
filepath =…How to Export a Conda Environment YAML File in Python
Generate a mock conda environment YAML export with a reusable Python function and the PyYAML library.
import yaml
def conda_env_mock(name="demo_env", channels=None, packages=None):
channels = channels or ["defaults"]
packages = packages or [
"python=3.11",
"pip",
"numpy=1.24.3",
"pandas=2.0.3",
]
env_dict = {
"name": name,
"channels": channels,
…How to Load envrc Files in Python
Parse and apply direnv-style envrc files to the current environment, with proper handling of variables, comments, and quotes.
import os
import tempfile
from pathlib import Path
from unittest.mock import patch
def load_envrc(envrc_path):
"""Parse an envrc-style file and apply it to the current environment."""
env_changes = {}
with open(envrc_path, "r") as f:
for line in f:
line = line.strip()
if l…How to build a tox multi-env matrix with mock config in Python
Simulate a tox multi-environment matrix by validating environment names and grouping extras into a readable matrix structure.
```python
import tox
def run_tox_matrix(mock_envs):
"""Simulate a tox multi-env configuration and verify mock choices."""
config = {
"tox": {
"envlist": mock_envs,
"config": {
"basepython": "python3.9",
"deps": ["pytest", "mock"],
},
…Dependency Injection in Python for Testability
Inject a config dependency into a service so you can swap a real environment-based config for a fake one in tests.
import os
class Config:
"""Simple config loader that can be easily faked in tests."""
def get(self, key, default=None):
return os.environ.get(key, default)
class UserService:
def __init__(self, config):
self.config = config
def get_timeout(self):
return int(self.config.get(…How to Test Environment Variables with pytest monkeypatch in Python
Shows how to use pytest's monkeypatch fixture to set and delete environment variables for isolated tests.
import os
import pytest
def get_database_url():
return os.getenv("DATABASE_URL", "postgres://default")
def test_database_url_with_env(monkeypatch):
monkeypatch.setenv("DATABASE_URL", "postgres://test-db")
assert get_database_url() == "postgres://test-db"
def test_database_url_default(monkeypatch):
m…How to Create a Deployment Environment Tag in Python
Generate a standardized deployment tag string by combining service and environment names with an f-string.
def mock_env_tag(service, environment):
return f"{service}-{environment}"
if __name__ == "__main__":
service = "api-gateway"
environment = "production"
tag = mock_env_tag(service, environment)
print(f"Deployment tag: {tag}")How to Check an External Gateway vs Use an Internal Mock in Python
This code checks whether an external network gateway is reachable using ping, then falls back to a deterministic internal mock for testing environments.
import subprocess
import sys
def check_external_gateway():
"""True if we can reach an external network target."""
try:
subprocess.run(
["ping", "-c", "1", "-W", "2", "8.8.8.8"],
capture_output=True,
timeout=3,
check=True,
)
return True
…How to Mock Hive Support in PySpark with unittest.mock
This code demonstrates how to mock Hive support in a PySpark environment using unittest.mock to simulate SQL queries returning fixed data.
from unittest.mock import Mock, patch
def get_hive_tables(spark):
"""Mock Hive support by returning a fixed list of tables."""
return spark.sql("SHOW TABLES").collect()
class HiveTable:
"""Simple class that mimics a Hive table row."""
def __init__(self, database, tableName):
self.database =…How to Implement a Data Helper Class in Python for Production Deployments
Build an environment-aware data helper in Python that loads config, extracts, transforms, and reports on JSON data using small, testable functions.
"""Production-style data helper for beginners.
Demonstrates:
- environment-aware config
- central data extraction
- small, testable functions
"""
import os
import json
from pathlib import Path
from typing import List, Dict, Any
def load_config(env: str = os.getenv("APP_ENV", "development")) -> Dict[str, Any]:
…How to Merge Helm Chart Values Per Environment in Python
Merge default Helm chart values with environment-specific overrides using a recursive dictionary merge function, then write each environment's YAML file.
from pathlib import Path
import json
import tempfile
DEFAULT_VALUES = {
"image": "nginx:latest",
"replicas": 1,
"resources": {"cpu": "100m", "memory": "128Mi"},
}
ENV_OVERRIDES = {
"dev": {"replicas": 1, "resources": {"cpu": "50m"}},
"staging": {"replicas": 2, "resources": {"cpu": "250m", "memor…How to simulate a database migration init container mock in Python
A mock init container that runs environment checks and a staged database migration job before the main application starts, printing progress to stdout.
```python
class MigrationJob:
def __init__(self, name, steps):
self.name = name
self.steps = steps
self.current_step = 0
self.status = "pending"
def run(self):
print(f"Initializing migration job: {self.name}")
for step in self.steps:
self.current_ste…Browse by section
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