Difference between method types in Python - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of instance method call

What is the output of this code when calling obj.instance_method()?

Python

class MyClass:
    def instance_method(self):
        return 'instance method called'

obj = MyClass()
print(obj.instance_method())

A TypeError: instance_method() missing 1 required positional argument: 'self'

B instance method called

C MyClass.instance_method

D None

💡 Hint

Instance methods receive the instance automatically as the first argument.

Instance methods receive the instance (obj) as the first argument named self, so calling obj.instance_method() works and returns the string.

❓ Predict Output

intermediate

Output of class method call

What is the output of this code when calling MyClass.class_method()?

Python

class MyClass:
    @classmethod
    def class_method(cls):
        return f'class method called from {cls.__name__}'

print(MyClass.class_method())

A None

B TypeError: class_method() missing 1 required positional argument: 'cls'

C class method called from MyClass

D class method called from cls

💡 Hint

Class methods receive the class itself as the first argument.

Class methods receive the class (MyClass) as the first argument named cls, so calling MyClass.class_method() returns the formatted string.

❓ Predict Output

advanced

Output of static method call

What is the output of this code when calling MyClass.static_method()?

Python

class MyClass:
    @staticmethod
    def static_method():
        return 'static method called'

print(MyClass.static_method())

A static method called

B TypeError: static_method() missing 1 required positional argument

C MyClass.static_method

D None

💡 Hint

Static methods do not receive any automatic first argument.

Static methods behave like regular functions inside the class namespace and do not receive self or cls automatically.

❓ Predict Output

advanced

Error when calling instance method on class

What error occurs when calling MyClass.instance_method() without an instance?

Python

class MyClass:
    def instance_method(self):
        return 'instance method called'

print(MyClass.instance_method())

A TypeError: instance_method() missing 1 required positional argument: 'self'

B AttributeError: 'MyClass' object has no attribute 'instance_method'

C instance method called

D None

💡 Hint

Instance methods require an instance to be called.

Calling an instance method on the class without passing an instance causes a TypeError because self is missing.

🧠 Conceptual

expert

Identify method type from behavior

Which method type does NOT receive any automatic first argument and behaves like a regular function inside the class?

A Instance method

B Class method

C Abstract method

D Static method

💡 Hint

Think about which method type does not get self or cls automatically.

Static methods do not receive self or cls automatically and behave like normal functions inside the class namespace.

Practice

1. Which method type in Python automatically receives the instance as the first argument named self?

easy

A. Instance method

B. Class method

C. Static method

D. Global function

Solution

1. Step 1: Understand method types

   Instance methods receive the instance as the first argument, usually named self.

2. Step 2: Identify method with self

   Class methods receive the class as cls, static methods receive no automatic first argument.

3. Final Answer:

   Instance method -> Option A

4. Quick Check:

   Method with self = Instance method [OK]

Hint: Look for self as first parameter for instance methods [OK]

Common Mistakes:

• Confusing cls with self
• Thinking static methods have self
• Mixing global functions with methods

2. Which decorator is used to define a class method in Python?

easy

A. @classmethod

B. @staticmethod

C. @instance

D. @class

Solution

1. Step 1: Recall Python decorators for methods

   Class methods use the @classmethod decorator to receive the class as the first argument.

2. Step 2: Identify correct decorator

   @staticmethod is for static methods, @instance and @class are invalid decorators.

3. Final Answer:

   @classmethod -> Option A

4. Quick Check:

   Class method decorator = @classmethod [OK]

Hint: Class methods always use @classmethod decorator [OK]

Common Mistakes:

• Using @staticmethod for class methods
• Assuming @instance is a valid decorator
• Confusing decorator names

3. What is the output of this code?

class MyClass:
    @staticmethod
    def greet():
        return 'Hello'

print(MyClass.greet())

medium

A. AttributeError

B. TypeError

C. None

D. 'Hello'

Solution

1. Step 1: Understand static method behavior

   Static methods do not require an instance or class argument and can be called directly on the class.

2. Step 2: Analyze the code output

   The static method greet returns the string 'Hello', so print(MyClass.greet()) outputs 'Hello'.

3. Final Answer:

   'Hello' -> Option D

4. Quick Check:

   Static method call returns 'Hello' [OK]

Hint: Static methods can be called on class without arguments [OK]

Common Mistakes:

• Expecting a TypeError for missing self
• Confusing static with instance method call
• Thinking static methods return None by default

4. Identify the error in this code:

class Example:
    @classmethod
    def show(cls):
        print(cls.value)

Example.show()

medium

A. Missing @staticmethod decorator

B. Method should use 'self' instead of 'cls'

C. Missing class attribute 'value'

D. Syntax error in method definition

Solution

1. Step 1: Check class method usage

   The method show is a class method and tries to print cls.value.

2. Step 2: Verify class attribute existence

   The class Example does not define value, so accessing cls.value causes an AttributeError at runtime.

3. Final Answer:

   Missing class attribute 'value' -> Option C

4. Quick Check:

   Class attribute missing causes error [OK]

Hint: Class methods need class attributes to access via cls [OK]

Common Mistakes:

• Confusing instance and class attributes
• Thinking @staticmethod fixes attribute errors
• Using 'self' in class methods incorrectly

5. You want a method that can be called on the class or instance but does NOT access instance or class data. Which method type should you use?

hard

A. Class method

B. Static method

C. Instance method

D. Property method

Solution

1. Step 1: Understand method access types

   Instance methods access instance data via self, class methods access class data via cls.

2. Step 2: Identify method without data access

   Static methods do not access instance or class data and can be called on both class and instance.

3. Final Answer:

   Static method -> Option B

4. Quick Check:

   No data access = Static method [OK]

Hint: No data access means use static method [OK]

Common Mistakes:

• Choosing instance or class method incorrectly
• Confusing property methods with static methods
• Assuming static methods access class data