API design & gRPC
REST best practices, protobuf, API versioning, and backward-compatible service contracts.
Convert Protobuf to JSON and Dict in Python
Provides static helper methods to convert between protobuf messages, JSON strings, and Python dictionaries using the google.protobuf library.
from google.protobuf.json_format import MessageToJson, Parse
import json
class DataConverter:
"""Helper class to convert between protobuf messages and common formats."""
@staticmethod
def to_json(message, indent=2):
"""Convert a protobuf message to JSON string."""
return MessageToJson(me…Create a Data Helper in Python for gRPC-style APIs
This code builds a simple DataHelper class that mimics gRPC request/response handling with in-memory storage, JSON serialization, and basic CRUD operations for beginners.
import json
from dataclasses import dataclass, asdict
from typing import Dict, Any
@dataclass
class User:
user_id: int
name: str
email: str
class DataHelper:
"""Simple helper to demonstrate gRPC-like data handling for beginners."""
def __init__(self) -> None:
self._users: Dict[int, Use…Format data in Python using dataclasses like gRPC messages
Convert Python dataclasses to and from dicts and format them gRPC-style for clean data handling.
from dataclasses import dataclass
from typing import Any, Dict, List, Optional
@dataclass
class ProductInfo:
"""Data class representing a gRPC-style product message."""
name: str
price: float
tags: List[str]
description: Optional[str] = None
def to_dict(self) -> Dict[str, Any]:
"""C…Generate an OpenAPI Spec from Mock Routes in Python
This Python script generates an OpenAPI 3.0 specification from a simple mock routes dictionary, mapping each HTTP method to response examples.
import json
from pathlib import Path
def generate_openapi_spec(routes: dict, title: str = "Mock API", version: str = "1.0.0") -> dict:
paths = {}
for route, methods in routes.items():
path_item = {}
for method, response_data in methods.items():
method = method.lower()
…How to Add HATEOAS Links to a Python API Response
Build a Python API resource class that adds self and next HATEOAS links to JSON responses, with a mock example for pagination.
import json
class Resource:
def __init__(self, name, data, next_page=None):
self.links = {"self": f"/api/resources/{name}"}
if next_page is not None:
self.links["next"] = f"/api/resources?page={next_page}"
self.data = data
def to_dict(self):
return {"links": self.…How to Add a Correlation ID Tracing Header in Python
A mock middleware generates or preserves a correlation ID header and logs structured JSON messages with it for API request tracing.
import uuid
import json
from dataclasses import dataclass, field
from typing import Optional
@dataclass
class Request:
headers: dict = field(default_factory=dict)
def get(self, key, default=None):
return self.headers.get(key, default)
class CorrelationIdMiddleware:
def __init__(self, header_name…How to Build a Data Helper Class in Python for Beginners
Create a beginner-friendly DataHelper class that stores, retrieves, filters, and summarizes records in a list of dictionaries.
from __future__ import annotations
import json
from dataclasses import dataclass, field
from typing import Any, Dict, List, Optional
@dataclass
class DataHelper:
"""A beginner-friendly helper for common data tasks."""
data: List[Dict[str, Any]] = field(default_factory=list)
def add_record(self, record…How to Build a Simple Data Helper in Python for API Design
Create a beginner-friendly DataHelper class that demonstrates basic CRUD operations (add, get, list, remove) using an in-memory dictionary, ideal for learning API design concepts.
class DataHelper:
"""Simple data helper for beginners learning API design concepts."""
def __init__(self):
self._data = {}
def add_record(self, key, value):
"""Add a record to the store."""
self._data[key] = value
return f"Added: {key} -> {value}"
def get_…How to Build a Simple Filter Helper in Python for API Design
Create a reusable data filter service with dataclasses that mimics gRPC request/response patterns for filtering dataset records.
from dataclasses import dataclass, field
from typing import List, Optional, Dict, Any
@dataclass
class FilterRequest:
"""A simple filter request mirroring a gRPC message structure."""
field_name: str
operator: str # eq, ne, gt, lt, contains
value: Any
page_size: int = 10
page_token: Optional…How to Build a Simple gRPC-Style Data Service in Python
Create a beginner-friendly gRPC-style service with dataclasses to simulate GetUser and CreateUser RPCs.
from dataclasses import dataclass
from typing import Optional
@dataclass
class User:
id: int
name: str
email: str
class UserService:
"""Simple gRPC-style service contract for beginner learners."""
def get_user(self, user_id: int) -> Optional[User]:
"""Simulated gRPC GetUser RPC."""
…How to Build a WebSocket Echo Server in Python with asyncio
Create a simple WebSocket echo server using the websockets library and asyncio to handle concurrent connections.
import asyncio
import websockets
async def echo(websocket):
async for message in websocket:
await websocket.send(f"Echo: {message}")
async def main():
async with websockets.serve(echo, "localhost", 8765):
print("WebSocket server started on ws://localhost:8765")
await asyncio.Future() …How to Create an RFC 7807 Error JSON in Python
Construct a structured error response using the RFC 7807 Problem Details format with a reusable function.
import json
from typing import Dict
def create_rfc7807_error(
type_: str,
title: str,
status: int,
detail: str,
instance: str,
extra_fields: Dict[str, object] | None = None,
) -> str:
"""
Build a JSON string following RFC 7807 Problem Details format.
"""
problem = {
"t…How to Decode Basic Auth Credentials in Python
Decode username and password from a Basic Auth header string using base64 and standard string operations.
import base64
def decode_basic_auth(header_value):
"""
Decode credentials from a Basic Auth header value.
Expected format: "Basic base64encoded(username:password)"
Returns a tuple (username, password).
"""
if not header_value.startswith("Basic "):
raise ValueError("Invalid Basic A…How to Expand Related Resources with a Mock Embed in Python
Simulate API response embedding by attaching mock embedded data to each related resource in a list using a simple Python class.
import json
class EmbedMock:
def __init__(self, resources):
self.resources = resources
def expand(self):
for resource in self.resources:
resource["embedded"] = self._generate_embed()
def _generate_embed(self):
return {
"id": 1,
"type": "mock",
…How to Implement Pagination with Offset and Limit in Python
A mock API pagination pattern that parses page and per_page query parameters, computes offset and limit, and slices a list of items for a specific page.
def paginate(items, page, per_page):
offset = (page - 1) * per_page
return items[offset:offset + per_page]
def parse_query_params(query_string):
params = {}
if query_string:
for pair in query_string.split("&"):
key, value = pair.split("=")
params[key] = value
page …How to Implement RBAC Permission Checks with a Route Decorator in Python
Build a reusable Python decorator that checks a user's role against allowed roles and raises a custom PermissionError when access is denied.
from functools import wraps
from enum import Enum
class Role(Enum):
ADMIN = "admin"
MODERATOR = "moderator"
USER = "user"
class PermissionError(Exception):
pass
def require_role(*allowed_roles):
def decorator(func):
@wraps(func)
def wrapper(user_role, *args, **kwargs):
…How to Implement Sparse Fieldsets in Python
A function that filters API responses by resource type, returning only requested fields plus IDs, as a sparse fieldset mock.
from dataclasses import dataclass, field
from typing import Dict, List, Optional
@dataclass
class MockResponse:
data: Dict[str, object] = field(default_factory=dict)
included: List[Dict[str, object]] = field(default_factory=list)
def select_fields(
data: Dict[str, object],
sparse_fields: Optional[D…How to Implement a PATCH Partial Update Merge Dict in Python
Implements a recursive merge function that applies HTTP PATCH-like partial updates to a nested dictionary while preserving untouched fields.
import json
def patch_merge(target: dict, patch: dict) -> dict:
"""Simulate HTTP PATCH semantic: shallow-merge patch into a copy of target."""
merged = target.copy()
for key, value in patch.items():
if isinstance(value, dict) and isinstance(merged.get(key), dict):
merged[key] = patch_m…How to Implement a REST DELETE Mock Server Returning 204 in Python
A minimal HTTP server mock that responds to DELETE requests with 204, 404, or 403 statuses based on the resource ID.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
class MockHandler(BaseHTTPRequestHandler):
def do_DELETE(self):
if self.path.startswith("/api/resource/"):
resource_id = self.path.split("/")[-1]
if resource_id == "42":
# Successful delete: 204 …How to Mock Content-Disposition and Extract Filename in Python
Parse and mock Content-Disposition headers in Python to extract filenames, handling both plain and RFC 5987 encoded values.
import os
from pathlib import Path
import re
from unittest.mock import patch
def get_filename_from_content_disposition(header_value):
"""
Extract filename from a Content-Disposition header value.
Supports both filename and filename* parameters (RFC 5987).
"""
if not header_value:
return No…How to Mock HTTP 304 Responses with If-None-Match in Python
Spin up a local HTTP server that returns a 304 Not Modified when a request carries a matching ETag, useful for testing cache behavior.
from http.server import BaseHTTPRequestHandler, HTTPServer
from threading import Thread
import urllib.request
ETAG = '"abc123"'
BODY = b'{"status": "ok"}'
class MockServer(BaseHTTPRequestHandler):
def do_GET(self):
if self.headers.get('If-None-Match') == ETAG:
self.send_response(304)
…How to Mock a GraphQL Query Type in Python
Create a lightweight mock of a GraphQL Query type to simulate repository lookups without a server.
import json
class Query:
def __init__(self):
self.starred_repos = [
{"id": 1, "name": "graphql", "owner": "graphql"}
]
def repository(self, name):
if name == "graphql":
return {"id": 1, "name": "graphql", "stargazerCount": 85000}
return None
if __name…How to Mock an API Key Header Authentication Server in Python
A minimal HTTP server that validates requests using an X-API-Key header and returns JSON responses for authenticated and unauthenticated calls.
import json
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
API_KEYS = {"test-user": "secret-key-123"}
class AuthHandler(BaseHTTPRequestHandler):
def do_GET(self):
auth = self.headers.get("X-API-Key")
if not auth or auth not in API_KEYS.values():
self.send_response…How to Parse gRPC Request Data in Python
Build a beginner-friendly gRPC service handler that parses incoming protobuf messages into Python dictionaries and starts a simple gRPC server.
from google.protobuf import json_format
import grpc
from concurrent import futures
import time
class DataParsingService:
def parse(self, request):
return {
"received_json": json_format.MessageToJson(request),
"parsed_fields": {
"name": request.name,
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API design & gRPC — Python code examples
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