Methods with parameters in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method with default and positional parameters

What is the output of this Python code?

Python

class Calculator:
    def multiply(self, x, y=2):
        return x * y

calc = Calculator()
print(calc.multiply(3))

A 6

B 3

C TypeError

D None

💡 Hint

Remember that y has a default value of 2 if not provided.

The method multiply takes x and y, with y defaulting to 2. Calling multiply(3) uses y=2, so 3*2=6.

❓ Predict Output

intermediate

Output when method parameters are passed by keyword

What will this code print?

Python

class Greeter:
    def greet(self, name, greeting='Hello'):
        print(f"{greeting}, {name}!")

g = Greeter()
g.greet(greeting='Hi', name='Alice')

A TypeError

B Hello, Alice!

C Hi, Alice!

D Hi, greeting!

💡 Hint

Check how keyword arguments match parameters.

The greet method is called with greeting='Hi' and name='Alice', so it prints 'Hi, Alice!'.

❓ Predict Output

advanced

Output of method with mutable default parameter

What is the output of this code?

Python

class Collector:
    def __init__(self):
        self.items = []
    def add(self, item, collection=[]):
        collection.append(item)
        return collection

c = Collector()
print(c.add('apple'))
print(c.add('banana'))

A ['apple']\n['banana']

B []\n[]

C TypeError

D ['apple']\n['apple', 'banana']

💡 Hint

Default mutable parameters keep their state between calls.

The default list 'collection' is shared between calls, so the second call appends 'banana' to the same list containing 'apple'.

❓ Predict Output

advanced

Output of method using *args and **kwargs

What does this code print?

Python

class Printer:
    def show(self, *args, **kwargs):
        print(args)
        print(kwargs)

p = Printer()
p.show(1, 2, a=3, b=4)

A (1, 2)\n{'a': 3, 'b': 4}

B [1, 2]\n{'a': 3, 'b': 4}

C TypeError

D (1, 2)\n[3, 4]

💡 Hint

*args collects positional arguments as a tuple, **kwargs collects keyword arguments as a dict.

The method prints the tuple of positional arguments and the dictionary of keyword arguments.

🧠 Conceptual

expert

Understanding parameter passing and object mutation

Consider this code. What is the output after calling modify_list?

Python

def modify_list(lst):
    lst.append(4)
    lst = [1, 2, 3]
    return lst

my_list = [0]
result = modify_list(my_list)
print(my_list)
print(result)

A [0]\n[1, 2, 3, 4]

B [0, 4]\n[1, 2, 3]

C [0, 4]\n[0, 4]

D [1, 2, 3]\n[1, 2, 3]

💡 Hint

Think about how lists are passed by reference and reassignment inside the function.

The original list 'my_list' is modified by append (so it becomes [0,4]). Then inside the function, lst is reassigned to a new list [1,2,3], which does not affect 'my_list'. The function returns the new list.

Practice

1. What is the purpose of parameters in a Python method?

easy

A. To accept inputs that the method can use

B. To store data permanently

C. To print output automatically

D. To create new variables outside the method

Solution

1. Step 1: Understand what parameters do

   Parameters allow a method to receive inputs when it is called.

2. Step 2: Identify the correct purpose

   Parameters are not for storing data permanently or printing output; they are for input.

3. Final Answer:

   To accept inputs that the method can use -> Option A

4. Quick Check:

   Parameters = inputs [OK]

Hint: Parameters let methods take inputs to work with [OK]

Common Mistakes:

• Thinking parameters store data permanently
• Confusing parameters with output
• Believing parameters create variables outside method

2. Which of the following is the correct way to define a method with two parameters a and b in Python?

easy

A. def my_method{a, b}:

B. def my_method[a, b]:

C. def my_method(a, b):

D. def my_method a, b:

Solution

1. Step 1: Recall Python method syntax

   Methods use parentheses () to list parameters separated by commas.

2. Step 2: Identify correct syntax

   Only def my_method(a, b): uses parentheses and commas correctly.

3. Final Answer:

   def my_method(a, b): -> Option C

4. Quick Check:

   Method parameters use ( ) and commas [OK]

Hint: Use parentheses and commas to list parameters [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Using curly braces instead of parentheses
• Omitting parentheses around parameters

3. What will be the output of the following code?

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

medium

A. Hello, name!

B. Error: name not defined

C. greet(Alice)

D. Hello, Alice!

Solution

1. Step 1: Understand the method call

   The method greet is called with argument "Alice" passed to parameter name.

2. Step 2: Evaluate the return statement

   The method returns the string "Hello, Alice!" using f-string formatting.

3. Final Answer:

   Hello, Alice! -> Option D

4. Quick Check:

   Method returns greeting with input name [OK]

Hint: Arguments replace parameters when method runs [OK]

Common Mistakes:

• Printing the parameter name instead of its value
• Confusing method name with output
• Expecting an error due to missing quotes

4. Find the error in this method definition:

def add_numbers(x, y)
    return x + y

medium

A. Parameters should be inside square brackets

B. Missing colon after parameter list

C. Return statement should be outside the method

D. Parameters must be strings

Solution

1. Step 1: Check method syntax

   Python method definitions require a colon ':' after the parameter list.

2. Step 2: Identify missing colon

   The code misses the colon after (x, y), causing syntax error.

3. Final Answer:

   Missing colon after parameter list -> Option B

4. Quick Check:

   Method header ends with ':' [OK]

Hint: Always put ':' after method parameters [OK]

Common Mistakes:

• Forgetting colon after parameters
• Using wrong brackets for parameters
• Misplacing return statement

5. You want to create a method calculate_area that takes two parameters width and height and returns their product. Which code correctly implements this?

hard

A. def calculate_area(width, height):
return width * height

B. def calculate_area(width, height):
return width + height

C. def calculate_area(width, height):
print(width * height)

D. def calculate_area(width, height):
return width / height

Solution

1. Step 1: Understand the method goal

   The method should return the product (multiplication) of width and height.

2. Step 2: Check each option's return value

   def calculate_area(width, height): return width * height returns width * height, which is correct. Others return sum, print output, or division.

3. Final Answer:

   def calculate_area(width, height):\n return width * height -> Option A

4. Quick Check:

   Area = width x height [OK]

Hint: Use * operator to multiply parameters for area [OK]

Common Mistakes:

• Using + instead of * for multiplication
• Printing instead of returning value
• Dividing instead of multiplying