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Python Code Samples

Medium snippets you can copy, study, and run in the browser editor.

5 matches
Streaming & messaging medium

How to Mock Offset Commit Auto vs Manual in Python

Demonstrates a Kafka-style offset commit function with auto/manual modes and tests it using unittest.mock.patch.

unittest mocking kafka
Python
from unittest.mock import Mock, patch

def commit_offsets(topic_partition_offsets, auto_commit=False):
    """Manually commit offsets or simulate auto-commit."""
    if auto_commit:
        print(f"Auto-committing offsets: {topic_partition_offsets}")
        return {"status": "auto_committed"}
    
    print(f"Manuall…
15 0 Open
Streaming & messaging medium

How to Mock a Kafka Producer Batch Send in Python

Simulate a Kafka producer in Python that sends batched JSON events with mock partitions and latency for testing streaming pipelines without a real broker.

kafka mock streaming
Python
import json
import random
import time
from datetime import datetime


class MockKafkaProducer:
    def __init__(self, topic):
        self.topic = topic
        self.sent_messages = []

    def send(self, value, key=None):
        message = {
            "topic": self.topic,
            "key": key,
            "value"…
13 0 Open
Streaming & messaging medium

How to Mock a Kafka Rebalance Listener in Python

Simulate Kafka consumer rebalance callbacks (on_partitions_revoked and on_partitions_assigned) with a mock consumer to test listener logic.

kafka rebalance mocking
Python
import time
from collections import defaultdict


class MockKafkaConsumer:
    def __init__(self):
        self.assignments = defaultdict(list)
        self.rebalances = 0

    def assign(self, partitions):
        self.rebalances += 1
        self.assignments.clear()
        for partition in partitions:
            s…
15 0 Open
Streaming & messaging medium

Kafka Consumer Poll Loop Mock in Python

Simulate a Kafka consumer poll loop with a mock class, process messages in batches, and commit offsets to understand streaming consumption patterns.

kafka streaming mock
Python
import time

class MockKafkaConsumer:
    def __init__(self, topic, messages):
        self.topic = topic
        self.messages = list(messages)
        self.position = 0

    def poll(self, timeout_ms=100):
        if self.position >= len(self.messages):
            time.sleep(timeout_ms / 1000)
            return []…
13 0 Open
Streaming & messaging medium

Mock Kafka Consumer Group Partition Assignment in Python

Simulates a Kafka consumer group's round-robin partition assignment with a Python class and prints assignments per consumer.

kafka consumer-group partition-assignment
Python
from collections import defaultdict


class ConsumerGroupAssignment:
    def __init__(self, group_name, topics_partitions):
        self.group_name = group_name
        self.consumers = {}
        self.assignments = defaultdict(set)
        topics_partitions = sorted(
            [(topic, partition) for topic, partiti…
14 0 Open

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