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Python Code Samples

Copy-ready Python snippets by topic and difficulty — short, focused, and runnable in the browser editor.

3 matches
Testing & modern typing easy

How to use unittest mock side_effect with a sequence in Python

Demonstrates using Mock.side_effect with a list to return different values per call and raise an exception at a specific call in unittest.

unittest mock side_effect
Python 
import unittest
from unittest.mock import Mock

class TestMockSideEffectSequence(unittest.TestCase):
    def test_side_effect_sequence(self):
        mock = Mock()
        mock.side_effect = [1, 2, 3, Exception("boom")]
        
        self.assertEqual(mock(), 1)
        self.assertEqual(mock(), 2)
        self.asser…
13 0 Open
A/B testing & experimentation easy

How to Create a Mock That Returns Inverse Counter Values in Python

Builds a Mock whose side_effect returns the inverse (1/count) of each Counter value, defaulting to 0.0 for unseen keys.

mock counter testing
Python 
from collections import Counter
from unittest.mock import Mock

def inverse_mock(counter: Counter) -> Mock:
    """
    Return a Mock that mimics the inverse of a Counter:
    each key returns a value representing the inverse of its count.
    The Mock's side_effect maps keys to their inverse counts.
    """
    mock …
13 0 Open
A/B testing & experimentation medium

How to Mock Sequential Calls in Python with unittest.mock

Use Mock.side_effect to return a different result for each sequential call and verify the call order with assert_has_calls.

mock unittest testing
Python 
import unittest
from unittest.mock import Mock

class Service:
    def fetch(self, item_id):
        raise NotImplementedError

def process_items(service, ids):
    results = []
    for item_id in ids:
        result = service.fetch(item_id)
        results.append(result)
    return results

if __name__ == "__main__":…
14 0 Open

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