Big data & Spark
PySpark jobs, partitioning, batch processing, and large-dataset transform patterns.
Accumulators Global Counter Mock in Python
Shows an accumulator-style global counter with a mock patch to control its value in tests.
import unittest
from unittest.mock import patch
# Module-level global counter accumulator
counter = 0
def increment(by=1):
"""Increment the global counter in place (accumulator pattern)."""
global counter
counter += by
return counter
def reset():
"""Reset the counter to zero."""
global count…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 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 a Catalyst Logical Plan in Python
Build a small Python class that mimics Spark Catalyst's logical plan tree for teaching or testing query optimizations.
from typing import Any, Dict, List, Optional
class CatalystLogicalPlan:
"""A minimal mock of Catalyst's logical plan for teaching purposes."""
def __init__(self, node_type: str, **kwargs: Any) -> None:
self.node_type = node_type
self.attributes: Dict[str, Any] = kwargs
self.child…How to Mock a Compute-Collect Action Trigger in Python
Mock a compute-collect action trigger using Python's unittest.mock to simulate Spark-style job execution and assert trigger behavior.
Here's a Python code sample for the problem title "Action trigger compute collect mock":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 Mock and Test a Rate-Limited Source Stream in Python
Build a class that rate-limits emitted items using a sliding window and test it with a simulated stream in Python.
import time
from collections import deque
class RateLimitedSource:
def __init__(self, max_rate, window=1.0):
self.max_rate = max_rate
self.window = window
self._timestamps = deque()
def emit(self, item):
now = time.monotonic()
while self._timestamps and self._timestam…How to use foreachBatch with a mock sink in PySpark
Demonstrates using Spark Structured Streaming's foreachBatch sink to capture and verify streaming batches by writing them into a custom mock sink object.
from pyspark.sql import SparkSession
from pyspark.sql.functions import col, lit
class MockSink:
def __init__(self):
self.batches = []
def write_batch(self, batch_df, batch_id):
# Collect batch data as list of dicts for verification
records = batch_df.collect()
self.batches…Browse by section
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Big data & Spark — Python code examples
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