Difference between method types in Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an instance method that prints the name.

Python

class Person:
    def __init__(self, name):
        self.name = name
    def show_name(self):
        print(self.[1])

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

Aself

Bname

CPerson

Dcls

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self' instead of 'name' inside print statement.

Using 'cls' which is for class methods.

Using 'Person' which is the class name, not an instance variable.

The instance method accesses the instance variable name using self.name.

2fill in blank

medium

Complete the code to define a class method that prints the class name.

Python

class Person:
    @classmethod
    def show_class(cls):
        print(cls.[1])

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

Aname

B__name__

C__class__

D__qualname__

Attempts:

3 left

💡 Hint

Common Mistakes

Using instance variable names like 'name'.

Using __class__ which is not an attribute of cls.

Using __name__ which is a module attribute.

The class method uses cls.__qualname__ to get the class's qualified name.

3fill in blank

hard

Fix the error in the static method that returns a greeting string.

Python

class Person:
    @staticmethod
    def greet():
        return 'Hello, ' + [1]

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

A'World'

Bcls.name

Cself.name

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access instance or class variables inside static method.

Using undefined variable 'name'.

Static methods do not receive self or cls, so use a fixed string like 'World'.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps words to their lengths only if length is greater than 3.

Python

words = ['apple', 'bat', 'carrot', 'dog']
lengths = {word: [1] for word in words if [2]

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

Alen(word)

Blen(word) > 3

Cword > 3

Dword.length

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'word > 3' which compares string to number.

Using 'word.length' which is not valid in Python.

The dictionary comprehension uses len(word) for values and filters words with length greater than 3.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase words to their lengths only if length is less than 6.

Python

words = ['apple', 'bat', 'carrot', 'dog']
result = [1]: [2] for word in words if [3]

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

Aword.upper()

Blen(word)

Clen(word) < 6

Dword.lower()

Attempts:

3 left

💡 Hint

Common Mistakes

Using word.lower() instead of uppercase.

Using wrong length condition like greater than 6.

The comprehension maps uppercase words to their lengths, filtering words shorter than 6 characters.

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