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How to Use prompt_toolkit Autocomplete in Python
Demonstrates an interactive command-line prompt with autocomplete using prompt_toolkit's WordCompleter and a mock dataset.
from prompt_toolkit import prompt
from prompt_toolkit.completion import WordCompleter
def main():
"""Demo of prompt_toolkit autocomplete with a mock dataset."""
# A simple mock "database" of programming languages
languages = [
"Python", "Java", "JavaScript", "TypeScript", "C++", "C#",
"Go"…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"],
},
…How to mock argparse nested subparsers in Python
Build an argparse parser with nested subparsers and test it using unittest.mock.patch for sys.argv and sys.stdout.
import argparse
from unittest.mock import patch
from io import StringIO
def build_parser():
parser = argparse.ArgumentParser(prog="app")
subparsers = parser.add_subparsers(dest="command", required=True)
# Outer subparser
outer = subparsers.add_parser("outer")
outer_sub = outer.add_subparsers(dest…Lint a Dockerfile with a Mock Hadolint in Python
A lightweight Python script that simulates hadolint by scanning Dockerfile text for common lint rules and printing violations.
import subprocess
import tempfile
from pathlib import Path
def lint_dockerfile(content: str) -> list[str]:
"""Mock hadolint by checking a few rules and returning violations."""
violations = []
lines = content.splitlines()
for idx, line in enumerate(lines, start=1):
stripped = line.strip()
…Mock Python version with unittest.mock.patch
Use unittest.mock.patch to simulate a specific Python version and test version-dependent behavior.
import sys
import unittest
from unittest.mock import patch
class TestPythonVersion(unittest.TestCase):
@patch("sys.version_info", (3, 9, 0, "final", 0))
def test_python_version_pinned(self):
self.assertEqual(sys.version_info[:2], (3, 9))
print(f"Pinned version: {sys.version_info.major}.{sys.ve…Mock pdm build and publish in Python
Simulate pdm build and publish commands with unittest.mock to test packaging workflows without triggering real builds or uploads.
from unittest.mock import Mock, patch
import pdm
def build_package() -> str:
"""Simulate building a package with pdm."""
build_mock = Mock(return_value="dist/mypackage-0.1.0-py3-none-any.whl")
with patch.object(pdm, "build", build_mock):
result = pdm.build()
return result
def publish_packa…Mock pip-compile to Resolve Requirements in Python
A mock function that mimics pip-compile by converting a requirements.in file into pinned, locked package versions.
import subprocess
import tempfile
from pathlib import Path
def compile_requirements_mock(requirements_in: str) -> str:
"""Mock pip-compile: resolve a simple requirements.in into a locked format."""
lines = [line.strip() for line in requirements_in.splitlines() if line.strip() and not line.startswith("#")]
…Mocking loguru for Structured Logging in Python
Simulate loguru's structured logging with a custom mock that captures JSON-formatted log entries with bound context.
import json
import sys
from io import StringIO
from unittest.mock import patch
def mock_loguru():
# Simulate a structured logger with context binding
class StructuredLogger:
def __init__(self):
self.context = {}
def bind(self, **kwargs):
logger = StructuredLogger()
…How to Mock anyio.run Backends (asyncio vs trio) in Python
Demonstrates how to mock anyio.run to verify backend selection (asyncio or trio) without actually running the event loop.
import anyio
from unittest.mock import Mock, patch
async def fetch_data():
await anyio.sleep(0.1)
return {"data": 42}
def run_with_backend(backend: str):
async def main():
result = await fetch_data()
print(f"[{backend}] Result: {result}")
anyio.run(main, backend=backend)
if __nam…How to Mock asyncio.open_connection in Python
Mock asyncio.open_connection with AsyncMock to test async code without a real network connection.
import asyncio
from unittest.mock import AsyncMock, patch
async def fetch_data(reader: asyncio.StreamReader) -> str:
data = await reader.readline()
return data.decode().strip()
async def main() -> None:
# Mock asyncio.open_connection to simulate a server response
mock_reader = AsyncMock()
mock_…How to Test HTTPX Async Client Pool Reuse with Mocks in Python
Mock an httpx.AsyncClient to verify connection pool reuse by asserting GET calls share a single client instance across concurrent async requests.
import asyncio
import httpx
from unittest.mock import AsyncMock, patch, Mock
async def fetch_with_pool(client, url, n_reuses=3):
results = []
for i in range(n_reuses):
resp = await client.get(url)
results.append(resp.status_code)
await asyncio.sleep(0) # yield to loop to mimic real us…Mocking Trio's open_nursery and spawn with asyncio.TaskGroup
Show how to mock Trio's nursery pattern using Python's asyncio.TaskGroup to simulate task spawning and completion.
import asyncio
class MockSpawner:
async def spawn(self, nursery):
print("Spawning mock task...")
await asyncio.sleep(1)
print("Mock task completed")
async def open_nursery():
async with asyncio.TaskGroup() as nursery:
mock = MockSpawner()
nursery.create_task(mock.spawn…Thread Pool Map for IO Bound Tasks in Python
Run IO-bound mock tasks concurrently with ThreadPoolExecutor.map and measure total elapsed time in Python.
import concurrent.futures
import time
from pathlib import Path
def mock_io_task(filename):
"""Simulate an IO-bound task by creating a small file and measuring its latency."""
path = Path(filename)
path.write_text("data")
time.sleep(0.1) # Simulate slow disk/network
return f"{filename} written in …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 Benchmark Python Code with pytest-benchmark and mocks
Use pytest-benchmark to measure function performance while combining Mock and patch for controlled test scenarios.
import time
from unittest.mock import Mock, patch
import pytest
from pytest_benchmark.fixture import BenchmarkFixture
def heavy_operation(data: list[int]) -> int:
"""Simulates a CPU-bound operation."""
return sum(x * x for x in data)
def test_heavy_operation_benchmark(benchmark: BenchmarkFixture) -> None:…How to Mock a Factory Boy Model Instance in Python
Create a factory boy factory, then patch its Meta.model with a Mock to control instance behavior in tests.
import factory
from dataclasses import dataclass
from unittest.mock import Mock, patch
import builtins
@dataclass
class User:
name: str
age: int
class UserFactory(factory.Factory):
class Meta:
model = User
name = "Alice"
age = 30
def get_user_name(user):
return user.name
def ma…How to Mock an Object Method in Python unittest
Mock a method on an instance or class with @patch.object, set its return value, and assert its call arguments in Python unittest.
import unittest
from unittest.mock import patch
class Calculator:
def add(self, a, b):
return a + b
def multiply(self, a, b):
return a * b
class TestCalculator(unittest.TestCase):
def test_add_normal(self):
calc = Calculator()
result = calc.add(2, 3)
self.asse…How to Mock and Stub API Calls in Playwright E2E Tests with Python
This code demonstrates how to mock and stub API responses in Playwright end-to-end tests using Python's unittest.mock patch and Playwright's APIRequestContext.
import re
from unittest.mock import patch
from playwright.sync_api import sync_playwright
def verify_api_mock(page, mock_url, mock_response):
with patch("playwright.sync_api.APIRequestContext.get") as mock_get:
mock_get.return_value.json.return_value = mock_response
mock_get.return_value.status_co…How to Mock open() in Python for Reading File Data
This example shows how to mock Python's built-in open() function using unittest.mock to simulate file reading without touching the disk.
import builtins
from unittest.mock import patch
def read_file_data(filename):
with open(filename, 'r') as f:
return f.read()
def mock_read_data():
fake_data = "This is mocked file content"
class FakeFile:
def __enter__(self):
return self
def __exit__(self, *args):…How to Mock pathlib Path.read_text with mock_open in Python
Mock pathlib.Path.read_text using patch and mock_open to test file-reading code without touching the filesystem.
import pathlib
from unittest.mock import mock_open, patch
def read_config(filepath: pathlib.Path) -> str:
"""Read file content with pathlib."""
return filepath.read_text()
if __name__ == "__main__":
mock_data = "version: 1.0\nname: demo-app"
with patch("pathlib.Path.open", mock_open(read_data=mo…How to Mock requests.get in Python
Mock requests.get with unittest.mock to test code that makes HTTP calls without hitting the network.
import requests
from unittest.mock import Mock, patch
def fetch_user_data(user_id):
response = requests.get(f"https://api.example.com/users/{user_id}")
return response.json()
def process_user(user_id):
mock_response = Mock()
mock_response.json.return_value = {"id": user_id, "name": "Alice", "age": 30…How to Mock return_value with MagicMock in Python unittest
Use unittest.mock.MagicMock to replace a dependency and set return_value to control what a mocked method returns during unit tests.
import unittest
from unittest.mock import MagicMock
class PaymentGateway:
def charge(self, amount):
raise NotImplementedError
class OrderService:
def __init__(self, gateway):
self.gateway = gateway
def process_order(self, amount):
return self.gateway.charge(amount)
class Test…How to Mock subprocess.run returncode in Python
Simulate subprocess.run return codes in tests with unittest.mock.patch and CompletedProcess.
import subprocess
from unittest.mock import patch
def run_command(cmd):
result = subprocess.run(cmd, capture_output=True, text=True)
return result.returncode
if __name__ == "__main__":
with patch("subprocess.run") as mock_run:
# Simulate a successful command (returncode 0)
mock_run.retu…How to Run an Integration Test with Docker Compose Mock in Python
Run a Python integration test against a docker-compose environment, using mocks to simulate service health and business logic responses.
import subprocess
import json
from typing import Dict
def run_integration_test() -> Dict[str, str]:
"""
Simulates an integration test against a docker-compose environment
using a mock service that returns canned responses.
"""
# Mock docker-compose environment check
env_ready = subprocess.run(…Browse by section
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