monkeypatch.delattr in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the attribute 'attr' from the object using monkeypatch.delattr.

PyTest

def test_remove_attr(monkeypatch):
    class Dummy:
        attr = 5
    obj = Dummy()
    monkeypatch.[1](Dummy, 'attr')
    assert not hasattr(obj, 'attr')

Drag options to blanks, or click blank then click option'

Aremoveattr

Bsetattr

Cdelattr

Dpatchattr

Attempts:

3 left

💡 Hint

Common Mistakes

Using setattr instead of delattr

Trying to remove attribute with a non-existent method

Forgetting to pass the object and attribute name

monkeypatch.delattr is used to delete an attribute from an object during testing.

2fill in blank

medium

Complete the code to delete the attribute 'value' from the class Example using monkeypatch.delattr.

PyTest

class Example:
    value = 10

def test_delete_value(monkeypatch):
    monkeypatch.[1](Example, 'value')
    assert not hasattr(Example, 'value')

Drag options to blanks, or click blank then click option'

Adelattr

Bsetattr

Cremove

Dpatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using setattr which sets attributes instead of deleting

Using a non-existent method like remove or patch

monkeypatch.delattr removes the specified attribute from the given object or class.

3fill in blank

hard

Fix the error in the code to correctly delete the attribute 'config' from the instance using monkeypatch.delattr.

PyTest

class Config:
    config = {'key': 'value'}

def test_config(monkeypatch):
    instance = Config()
    monkeypatch.[1](Config, 'config')
    assert not hasattr(instance, 'config')

Drag options to blanks, or click blank then click option'

Aremoveattr

Bdelattrt

Cdel_attr

Ddelattr

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the method name

Using underscores or extra letters in the method name

The correct method name is monkeypatch.delattr to delete attributes.

4fill in blank

hard

Fill both blanks to delete the attribute 'setting' from the object and verify it is removed.

PyTest

class Settings:
    setting = True

s = Settings()
monkeypatch.[1](Settings, [2])
assert not hasattr(s, 'setting')

Drag options to blanks, or click blank then click option'

Adelattr

Bsetting

C'setting'

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Passing attribute name without quotes

Using wrong method name

Passing attribute name as variable instead of string

Use monkeypatch.delattr to delete the attribute, passing the attribute name as a string.

5fill in blank

hard

Fill all three blanks to delete the attribute 'flag' from the class and check it is gone.

PyTest

class Feature:
    flag = False

monkeypatch.[1](Feature, [2])
assert not hasattr(Feature, [3])

Drag options to blanks, or click blank then click option'

Adelattr

B'flag'

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove instead of delattr

Passing attribute name without quotes

Using different strings for deletion and check

monkeypatch.delattr deletes the attribute; the attribute name must be passed as a string.

Practice

1. What is the main purpose of monkeypatch.delattr in pytest?

easy

A. To temporarily remove an attribute from an object during a test

B. To permanently delete a file during testing

C. To add a new attribute to an object during a test

D. To reset all attributes of an object to default values

Solution

1. Step 1: Understand monkeypatch.delattr functionality

   It temporarily removes an attribute from an object only during the test execution.

2. Step 2: Compare with other options

   Options B, C, and D describe different actions unrelated to temporary attribute removal.

3. Final Answer:

   To temporarily remove an attribute from an object during a test -> Option A

4. Quick Check:

   monkeypatch.delattr = temporary attribute removal [OK]

Hint: Remember: delattr means deleting attribute temporarily [OK]

Common Mistakes:

• Confusing delattr with adding attributes
• Thinking it deletes files or permanent changes
• Assuming it resets attributes instead of removing

2. Which of the following is the correct syntax to remove the attribute foo from object obj using monkeypatch in pytest?

easy

A. monkeypatch.delattr('foo', obj)

B. monkeypatch.delattr(obj.foo)

C. monkeypatch.delattr('obj', foo)

D. monkeypatch.delattr(obj, 'foo')

Solution

1. Step 1: Recall monkeypatch.delattr syntax

   The correct syntax requires the object and the attribute name as a string: monkeypatch.delattr(object, 'attribute_name').

2. Step 2: Analyze options

   monkeypatch.delattr(obj, 'foo') matches the correct syntax. Options A, C, and D misuse argument order or types.

3. Final Answer:

   monkeypatch.delattr(obj, 'foo') -> Option D

4. Quick Check:

   delattr(object, 'attr') syntax = monkeypatch.delattr(obj, 'foo') [OK]

Hint: Use object first, then attribute name as string [OK]

Common Mistakes:

• Passing attribute without quotes
• Swapping object and attribute order
• Passing attribute as variable instead of string

3. Given the code below, what will happen when test_func runs?

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

def test_func(monkeypatch):
    obj = MyClass()
    monkeypatch.delattr(obj, 'greet')
    try:
        obj.greet()
    except AttributeError:
        print('Attribute missing')

medium

A. Prints 'Hello'

B. Does nothing and passes silently

C. Raises AttributeError and prints 'Attribute missing'

D. Raises TypeError

Solution

1. Step 1: Understand monkeypatch.delattr effect

   It removes the 'greet' method from obj temporarily during the test.

2. Step 2: Analyze the try-except block

   Calling obj.greet() after removal raises AttributeError, caught and prints 'Attribute missing'.

3. Final Answer:

   Raises AttributeError and prints 'Attribute missing' -> Option C

4. Quick Check:

   Removed attribute causes AttributeError caught and message printed [OK]

Hint: Removed method causes AttributeError when called [OK]

Common Mistakes:

• Expecting original method to run after deletion
• Confusing AttributeError with TypeError
• Ignoring exception handling block

4. You wrote this test code but it raises an error:

def test_example(monkeypatch):
    class Sample:
        def method(self):
            return 42
    obj = Sample()
    monkeypatch.delattr('obj', 'method')
    obj.method()

What is the error and how to fix it?

medium

A. Error: SyntaxError; fix by adding parentheses to method call

B. Error: AttributeError; fix by changing 'obj' to obj in delattr

C. Error: TypeError; fix by removing quotes around 'method'

D. Error: NameError; fix by defining obj before delattr

Solution

1. Step 1: Identify incorrect delattr usage

   Passing 'obj' as a string instead of the object causes AttributeError because monkeypatch expects the object itself.

2. Step 2: Correct the argument

   Change monkeypatch.delattr('obj', 'method') to monkeypatch.delattr(obj, 'method') to pass the actual object.

3. Final Answer:

   Error: AttributeError; fix by changing 'obj' to obj in delattr -> Option B

4. Quick Check:

   Pass object, not string, to delattr [OK]

Hint: Pass object, not string, as first argument [OK]

Common Mistakes:

• Passing object name as string instead of object
• Misplacing quotes around attribute name
• Ignoring error message details

5. You want to test how your code behaves when a method calculate is missing from an object calculator. Which pytest monkeypatch.delattr usage correctly simulates this scenario and allows you to assert the error handling?

hard

A. monkeypatch.delattr(calculator, 'calculate') before calling the method and assert AttributeError

B. monkeypatch.delattr(calculator, 'calculate') after calling the method to check result

C. monkeypatch.setattr(calculator, 'calculate', lambda: 0) to replace method

D. monkeypatch.delattr('calculator', 'calculate') to remove method

Solution

1. Step 1: Understand test goal

   You want to simulate the absence of 'calculate' method to test error handling.

2. Step 2: Apply monkeypatch.delattr correctly

   Removing 'calculate' before calling it triggers AttributeError, which you can assert. monkeypatch.delattr(calculator, 'calculate') before calling the method and assert AttributeError does this correctly.

3. Step 3: Analyze other options

   monkeypatch.delattr(calculator, 'calculate') after calling the method to check result removes method after call (too late). monkeypatch.setattr(calculator, 'calculate', lambda: 0) to replace method replaces method, not removes. monkeypatch.delattr('calculator', 'calculate') to remove method passes object name as string (incorrect).

4. Final Answer:

   monkeypatch.delattr(calculator, 'calculate') before calling the method and assert AttributeError -> Option A

5. Quick Check:

   Remove method before call to test missing attribute [OK]

Hint: Remove attribute before call to test missing method [OK]

Common Mistakes:

• Removing attribute after method call
• Replacing method instead of removing
• Passing object name as string instead of object