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How to Mock an API Gateway Router in Python
Create a lightweight HTTP server that routes requests to mock microservice responses, simulating an API gateway for local development and testing.
from http.server import HTTPServer, BaseHTTPRequestHandler
import json
class SimpleGateway(BaseHTTPRequestHandler):
def do_GET(self):
routes = {
"/users": {"service": "user-service", "status": "ok", "count": 42},
"/orders": {"service": "order-service", "status": "ok", "count": 17}…How to Mock an Ambassador Edge Proxy in Python
Build a lightweight mock Ambassador edge proxy with Python's http.server that responds to health and user endpoint requests for local development and testing.
import http.server
import json
import urllib.parse
import threading
class AmbassadorProxyHandler(http.server.BaseHTTPRequestHandler):
def do_GET(self):
parsed = urllib.parse.urlparse(self.path)
if parsed.path == "/health":
self.send_response(200)
self.send_header("Content-T…How to Order Partition Key Events in Python (Mock Stream)
Generate a mock event stream grouped by partition key and sort it deterministically by key then sequence in Python.
import itertools
import random
def partition_key_events(keys, events_per_key=3, seed=None):
"""Produce a realistic-looking, but mock, event stream grouped by partition key.
Args:
keys: iterable of partition keys (e.g. strings or ints).
events_per_key: how many events we want per key.
…How to Use the Adapter Pattern to Mock a Legacy System in Python
This code demonstrates the Adapter pattern, allowing a modern interface to interact with a legacy system by wrapping its outdated method.
class LegacySystem:
def legacy_method(self, data):
return f"Legacy processed: {data}"
class ModernInterface:
def process(self, data):
raise NotImplementedError
class Adapter(ModernInterface):
def __init__(self, legacy):
self.legacy = legacy
def process(self, data):
re…How to implement read-your-writes sticky routing in Python
A mock StickyRouter class that routes all requests for the same key to the same node, ensuring read-after-write consistency.
import random
class StickyRouter:
def __init__(self, nodes):
self.nodes = nodes
self.routes = {}
def route(self, key):
if key not in self.routes:
self.routes[key] = random.choice(self.nodes)
return self.routes[key]
def read(self, key):
node = self.rout…How to implement round-robin load balancing in Python
Implement a client-side round-robin load balancer that distributes requests sequentially across a list of mock servers using itertools.cycle.
import itertools
import random
class MockServer:
def __init__(self, name):
self.name = name
def handle_request(self, request_id):
return f"Server {self.name} handled request #{request_id}"
class RoundRobinLoadBalancer:
def __init__(self, servers):
self.servers = servers
…How to mock a SPIFFE workload identity in Python
Generate a mock SPIFFE ID and token for a workload using a trust domain, namespace, and service account.
import hashlib
import json
from dataclasses import dataclass, asdict
@dataclass
class SPIFFEIdentity:
trust_domain: str
namespace: str
service_account: str
@property
def id(self) -> str:
return f"spiffe://{self.trust_domain}/ns/{self.namespace}/sa/{self.service_account}"
def mock_workl…How to mock an external service in Python with an anti-corruption facade
This code implements an anti-corruption facade that mocks an external API, allowing client code to interact with a simulated service while keeping the same interface.
class AntiCorruptionFacade:
"""Mocks a real API while keeping the same interface."""
def __init__(self, data_store):
self._data_store = data_store
self._calls = []
def get_user(self, user_id):
self._calls.append(f"get_user({user_id})")
return self._data_store.get(u…How to Broadcast a Small Lookup Table in Python
Simulates broadcasting a small lookup table by iterating key-value pairs and emitting packed rows to subscribers with deterministic output.
import random
# Generate a deterministic mock broadcast of a small lookup table
# with 5 keys and random integer values (seeded for reproducibility)
data = {
"sensor_a": 22,
"sensor_b": 87,
"sensor_c": 43,
"sensor_d": 65,
"sensor_e": 31,
}
# Simulate a broadcast to subscribers by iterating and p…How to Create a Mock Kafka Producer in Python
Build a Kafka producer that generates mock streaming records with JSON serialization and error handling for local testing.
import json
import time
from kafka import KafkaProducer
from kafka.errors import KafkaError
def create_mock_producer(bootstrap_servers="localhost:9092", topic="input-topic"):
"""Create a Kafka producer that generates mock streaming data."""
producer = KafkaProducer(
bootstrap_servers=bootstrap_servers…How to Explode an Array Column in Python
This code demonstrates a mock explode operation that converts an array column into multiple rows, similar to Spark's explode function.
import json
def explode_array_column(data, column):
"""Mock explode: split array column into multiple rows."""
exploded = []
for row in data:
values = row.get(column, [])
for value in values:
new_row = dict(row)
new_row[column] = value
exploded.append(n…How to Filter and Project Spark DataFrames with PySpark SQL
Simulate a SQL SELECT with WHERE using PySpark DataFrame select and filter to project columns and apply conditions.
from pyspark.sql import SparkSession
from pyspark.sql.functions import col
spark = SparkSession.builder.appName("QueryFilterMock").master("local[2]").getOrCreate()
data = [
("Alice", 28, "Engineering"),
("Bob", 35, "Sales"),
("Carol", 32, "Engineering"),
("David", 25, "Marketing"),
("Eve", 29, "E…How to Implement MapReduce Word Count in Python Using a Dict
Simulate a MapReduce word count pipeline in Python with a mock dict, splitting text into words, shuffling, and reducing to frequency counts.
def map_reduce_word_count(text: str) -> dict:
"""Simulate a MapReduce pipeline to count word frequencies."""
# MAP phase: split into words and emit (word, 1) pairs
mapped = []
for word in text.lower().split():
# Clean word of punctuation
clean_word = ''.join(char for char in word if cha…How to Implement collect_list in Python
Group rows by a key and collect all corresponding values into a list — a pure-Python mock of Spark's collect_list aggregation.
from collections import defaultdict
def collect_list(rows, key_field, value_field):
grouped = defaultdict(list)
for row in rows:
grouped[row[key_field]].append(row[value_field])
return dict(grouped)
if __name__ == "__main__":
data = [
{"dept": "sales", "emp": "alice"},
{"dept"…How to Mock DataFrame Schema Columns in Python
Create an empty pandas DataFrame with only the specified column names to mock a schema before any data is loaded.
import pandas as pd
def mock_schema(columns):
return pd.DataFrame(columns=columns)
if __name__ == "__main__":
cols = ["name", "age", "city"]
df = mock_schema(cols)
print(df)
print(f"Columns: {list(df.columns)}, Shape: {df.shape}")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 Mock Partition Pruning in Python
A dataclass-based mock that filters partitions by year and month to emulate Spark's partition pruning logic.
from dataclasses import dataclass
from typing import List
@dataclass(frozen=True)
class Partition:
id: int
year: int
month: int
class PartitionPruner:
"""Mock partition pruning: only keep partitions that match the filter."""
def __init__(self, partitions: List[Partition]):
self._partiti…How to Mock a File Source Watch Directory in Python
Poll a directory for new files and log changes, simulating a watch directory for data ingestion patterns.
import os
import time
from pathlib import Path
def watch_directory(dir_path: str, poll_interval: float = 1.0, max_iterations: int = 5):
"""
Mock a file-source watch directory by polling for changes.
Returns new files detected during each poll cycle.
"""
directory = Path(dir_path)
directory.mk…How to Mock a Hash Join on Large and Small Tables in Python
This code efficiently joins a large dataset (1000 rows) with a small lookup table (20 rows) by building a dictionary hash lookup, mimicking a hash join strategy used in big data systems.
import random
from pprint import pprint
# Large table: 1000 rows (id, group_id, value)
large = [{"id": i, "group_id": random.randint(1, 20), "value": random.random() * 100} for i in range(1000)]
# Small table: 20 rows (group_id, label)
small = [{"group_id": g, "label": f"Group-{g}"} for g in range(1, 21)]
# Mock a …How to Mock a Socket Stream in Python
Simulate a streaming socket source with a generator to test stream-read and buffering logic without a real network.
import socket
import threading
import time
def mock_socket_stream(data_chunks, delay=0.1):
"""Generator that simulates a streaming socket source."""
for chunk in data_chunks:
time.sleep(delay)
yield chunk
def read_stream_socket(stream_gen):
"""Reads from mock stream and prints received ch…How to Mock a User-Defined Function (UDF) in Python
Wrap a real UDF implementation with call logging to simulate and track invocations in a data pipeline.
from typing import Any, Callable
# Mock a user-defined function (UDF) that was previously complex or external
def mock_udf(name: str, implementation: Callable[..., Any], *, calls: list[Any]) -> Callable[..., Any]:
"""Wrap a real implementation with call logging to simulate a UDF."""
def wrapper(*args: Any, *…How to Pivot and Group Aggregate in Python
Group records by a key, collect values, and apply an aggregate function (like sum) to build a pivot-style summary dictionary.
from collections import defaultdict
def pivot_group_aggregate(records, group_key, value_key, agg_func):
groups = defaultdict(list)
for record in records:
groups[record[group_key]].append(record[value_key])
return {key: agg_func(values) for key, values in groups.items()}
if __name__ == "__main__":…How to Shuffle Items by Group in Python
Randomly shuffle items within each group while keeping groups contiguous, using a seed for reproducible results.
import random
def shuffle_sort_groups(items, group_key, seed=None):
"""Randomize order within groups, keeping groups contiguous."""
rng = random.Random(seed)
groups = {}
for item in items:
key = group_key(item)
groups.setdefault(key, []).append(item)
result = []
for k…How to Truncate Lineage Back to a Checkpoint in Python
Walks a linked list of lineage nodes upward to find the nearest checkpoint and returns that node, truncating the lineage.
class LineageNode:
def __init__(self, name, parent=None, checkpoint=None):
self.name = name
self.parent = parent
self.checkpoint = checkpoint
def truncate_at_checkpoint(self):
"""Truncate lineage back to the last checkpoint."""
current = self
while current.check…Browse by section
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