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Detect Circular Imports Across Python Projects Automatically
This script walks through all .py files in a directory, builds an import graph, and uses depth-first search to find cycles—printing each circular dependency chain.
import ast
import sys
from pathlib import Path
from collections import defaultdict, deque
def find_imports(filepath):
"""Return set of module names imported by a Python file."""
imports = set()
try:
with open(filepath) as f:
tree = ast.parse(f.read())
except (SyntaxError, UnicodeDe…How to Generate a Dependency Graph for Python Projects
This script walks through a Python project directory, parses each .py file's imports, and prints a dependency graph showing which modules depend on which other modules.
import os
import ast
from pathlib import Path
from collections import defaultdict
def get_imports(filepath):
with open(filepath) as f:
try:
tree = ast.parse(f.read())
except SyntaxError:
return []
imports = []
for node in ast.walk(tree):
if isinstance(node, …How to Use Stubs, Fakes, Spies, and Mocks in Python Testing
Implement four types of test doubles — stubs, fakes, spies, and mocks — as subclasses of a PaymentGateway interface to replace real dependencies during testing.
class PaymentGateway:
def charge(self, amount):
raise NotImplementedError
class StubPaymentGateway(PaymentGateway):
"""Returns a fixed response without any logic."""
def charge(self, amount):
return {"success": True, "transaction_id": "stub-12345"}
class FakePaymentGateway(PaymentGatewa…How to Apply the Clean Architecture Dependency Rule in Python
Demonstrates the dependency rule with a Protocol repository, a use case, and a presenter wired together at a composition root.
from dataclasses import dataclass
from typing import List, Protocol
class Repository(Protocol):
def get_items(self) -> List[str]:
...
@dataclass
class InMemoryRepository:
items: List[str]
def get_items(self) -> List[str]:
return self.items
class UseCase:
"""Application layer depends…How to Build an Adapter to Translate External API Responses in Python
Build an adapter class that translates a mock external API's response shape into your internal representation, keeping callers decoupled from the external contract.
import json
from typing import Dict, Any
class ExternalAPI:
"""Mock external service returning a different data shape."""
def get_user(self, user_id: int) -> Dict[str, Any]:
return {
"id": user_id,
"full_name": "Jane Doe",
"email_address": "jane@example.com",
…How to Migrate a Legacy Facade with the Strangler Fig Pattern in Python
Use a facade to wrap a legacy API and incrementally migrate callers to a modern interface, following the strangler fig pattern.
class LegacyAPI:
"""Simulates the legacy system's raw interface."""
def get_user(self, user_id):
return {"id": user_id, "name": "Alice", "legacy": True}
class UserService:
"""Facade that wraps the legacy system with a modern interface."""
def __init__(self, legacy_api=None):
self.lega…How to Mock a Timeout per Dependency Call in Python
This code demonstrates how to simulate and test per-call timeouts for external dependencies using Python's unittest.mock and a simple timing wrapper.
```python
import time
from unittest.mock import Mock, patch
def call_dependency(dependency, timeout):
start = time.time()
result = dependency.call()
elapsed = time.time() - start
if elapsed > timeout:
raise TimeoutError(f"Dependency call took {elapsed:.2f}s, exceeding timeout {timeout}s")
…How to Implement Graceful Degradation with Feature Disabling in Python
A pattern that disables enhanced features and falls back to basic functionality when a dependency fails, with mock-based testing.
import random
from unittest.mock import patch
class EnhancedFeature:
"""A feature that can gracefully degrade when a dependency is unavailable."""
def __init__(self):
self.feature_enabled = True
def get_enhanced_data(self):
"""Simulate an enhanced feature that depends on external data."…Training Pipeline Orchestration Mock DAG in Python
Build a mock DAG orchestrator that runs ML pipeline stages in dependency order using topological sorting (Kahn's algorithm).
from collections import deque
from dataclasses import dataclass, field
@dataclass
class DAGNode:
name: str
task: callable
dependencies: list[str] = field(default_factory=list)
class MockDAG:
def __init__(self, nodes: list[DAGNode]):
self.nodes = {n.name: n for n in nodes}
self.execu…Browse by section
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