monkeypatch.delattr in PyTest

Introduction

monkeypatch.delattr helps you remove an attribute from an object during a test. This lets you test how your code behaves when that attribute is missing.

You want to test how your code reacts if a method or property is missing from an object.

You need to simulate an environment where a certain attribute does not exist.

You want to check error handling when an expected attribute is deleted.

You want to isolate tests by removing attributes temporarily without changing real code.

Syntax

PyTest

monkeypatch.delattr(target, name, raising=True)

target is the object or module from which you want to remove an attribute.

name is the string name of the attribute to remove.

raising controls if an error is raised when the attribute does not exist (default is True).

Examples

Removes the attribute some_method from some_object. Raises error if attribute not found.

PyTest

monkeypatch.delattr(some_object, 'some_method')

Removes some_property from module. Does not raise error if attribute is missing.

PyTest

monkeypatch.delattr(module, 'some_property', raising=False)

Sample Program

This test removes the greet method from MyClass. Then it tries to call greet on an instance. Since the method is removed, it catches the AttributeError and prints a message.

PyTest

import pytest

class MyClass:
    def greet(self):
        return 'Hello'

def test_greet_missing(monkeypatch):
    obj = MyClass()
    # Remove greet method from the class
    monkeypatch.delattr(MyClass, 'greet')
    try:
        obj.greet()
    except AttributeError:
        print('greet method is missing')
    else:
        print('greet method exists')

Important Notes

Use raising=False if you want to avoid errors when the attribute might not exist.

monkeypatch.delattr only affects the object during the test run, so your real code stays unchanged.

It is useful to test error handling and fallback logic when attributes are missing.

Summary

monkeypatch.delattr removes an attribute from an object temporarily during tests.

It helps simulate missing methods or properties to test error handling.

Use it to make your tests more robust and realistic.