Function definition and syntax in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a function with default and keyword arguments

What is the output of this Python code?

Python

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

print(greet("Alice"))
print(greet("Bob", greeting="Hi"))

A Hello, Alice!\nHello, Bob!

B Hello, Alice!\nHi, Bob!

C Hi, Alice!\nHi, Bob!

D Error: missing required positional argument

💡 Hint

Check how default arguments work and how keyword arguments override them.

The function greet has a default greeting 'Hello'. Calling greet('Alice') uses the default. Calling greet('Bob', greeting='Hi') overrides the default with 'Hi'.

❓ Predict Output

intermediate

Return value of a function with multiple return statements

What is the output of this code?

Python

def check_number(x):
    if x > 0:
        return "Positive"
    elif x == 0:
        return "Zero"
    else:
        return "Negative"

print(check_number(-5))

A Negative

B Zero

C Positive

D None

💡 Hint

Look at the input value and which condition it satisfies.

The input -5 is less than zero, so the function returns 'Negative'.

📝 Syntax

advanced

Identify the syntax error in function definition

Which option contains a syntax error in the function definition?

A def add(a, b):\n return a + b

B def divide(a, b):\n return a / b

C def multiply(a, b)\n return a * b

D def subtract(a, b):\n return a - b

💡 Hint

Check for missing colons in function headers.

Option C is missing a colon ':' after the function parameters, causing a syntax error.

❓ Predict Output

advanced

Output of a function using *args and **kwargs

What is the output of this code?

Python

def info(*args, **kwargs):
    return f"Args: {args}, Kwargs: {kwargs}"

print(info(1, 2, 3, name='Alice', age=30))

A Args: (1, 2, 3), Kwargs: {'name': 'Alice', 'age': 30}

B Args: [1, 2, 3], Kwargs: {'name': 'Alice', 'age': 30}

C Args: (1, 2, 3), Kwargs: [('name', 'Alice'), ('age', 30)]

D Args: 1, 2, 3, Kwargs: name='Alice', age=30

💡 Hint

Remember that *args collects positional arguments as a tuple and **kwargs collects keyword arguments as a dictionary.

The *args parameter collects positional arguments into a tuple. The **kwargs parameter collects keyword arguments into a dictionary.

🧠 Conceptual

expert

Effect of mutable default arguments in function definitions

What will be the output after running this code?

Python

def append_item(item, lst=[]):
    lst.append(item)
    return lst

print(append_item(1))
print(append_item(2))

A [1]\n[2]

B Error: mutable default argument

C [1]\n[1]

D [1]\n[1, 2]

💡 Hint

Think about how default mutable arguments behave across multiple function calls.

The default list is created once and shared across calls. So the second call appends 2 to the same list that already contains 1.

Practice

1. What keyword do you use to start defining a function in Python?

easy

A. function

B. define

C. func

D. def

Solution

1. Step 1: Recall Python function syntax

   In Python, functions are defined using the keyword def.

2. Step 2: Compare options

   Only def uses the correct keyword def. Others are not valid Python keywords.

3. Final Answer:

   def -> Option D

4. Quick Check:

   Function definition starts with def [OK]

Hint: Remember: def starts every function in Python [OK]

Common Mistakes:

• Using 'function' instead of 'def'
• Using 'func' or 'define' which are not Python keywords

2. Which of the following is the correct syntax to define a function named greet that takes no parameters?

easy

A. def greet():

B. function greet():

C. def greet[]:

D. def greet:

Solution

1. Step 1: Check function header syntax

   The correct syntax uses def, function name, parentheses for parameters, and a colon.

2. Step 2: Validate each option

   def greet(): matches this exactly: def greet():. Others have wrong keywords, brackets, or missing parentheses.

3. Final Answer:

   def greet(): -> Option A

4. Quick Check:

   def + name + () + : is correct syntax [OK]

Hint: Function name + () + : after def is always needed [OK]

Common Mistakes:

• Omitting parentheses after function name
• Using square brackets instead of parentheses
• Using 'function' keyword instead of 'def'

3. What will be the output of this code?

def add(x, y):
    return x + y

print(add(3, 4))

medium

A. 7

B. 34

C. TypeError

D. None

Solution

1. Step 1: Understand function behavior

   The function add takes two numbers and returns their sum.

2. Step 2: Calculate the return value

   Calling add(3, 4) returns 3 + 4 = 7, which is printed.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Return sends back the sum; print shows it [OK]

Common Mistakes:

• Concatenating numbers as strings (getting '34')
• Forgetting to return value (getting None)
• Passing wrong number of arguments causing TypeError

4. Find the error in this function definition:

def multiply(a, b)
    return a * b

medium

A. Indentation error in return statement

B. Missing colon at the end of function header

C. Wrong function name

D. Parameters should be in square brackets

Solution

1. Step 1: Check function header syntax

   The function header must end with a colon (:).

2. Step 2: Identify missing colon

   The code misses the colon after def multiply(a, b), causing a syntax error.

3. Final Answer:

   Missing colon at the end of function header -> Option B

4. Quick Check:

   Function header must end with : [OK]

Hint: Always put : after function header line [OK]

Common Mistakes:

• Forgetting colon after function header
• Incorrect indentation of return line
• Using wrong brackets for parameters

5. You want to write a function is_even that returns True if a number is even, otherwise False. Which is the correct function?

hard

A. def is_even(n):
return n % 2

B. def is_even(n):
return n / 2 == 0

C. def is_even(n):
if n % 2 == 0:
return True
else:
return False

D. def is_even(n):
if n % 2:
return True
else:
return False

Solution

1. Step 1: Understand even number check

   A number is even if remainder when divided by 2 is zero (n % 2 == 0).

2. Step 2: Evaluate each option

   def is_even(n): if n % 2 == 0: return True else: return False correctly returns True if remainder is zero, else False. def is_even(n): return n / 2 == 0 uses division instead of modulo. def is_even(n): if n % 2: return True else: return False returns True when remainder is non-zero (odd). def is_even(n): return n % 2 returns remainder directly (not boolean).

3. Final Answer:

   def is_even(n): if n % 2 == 0: return True else: return False -> Option C

4. Quick Check:

   Use modulo == 0 to check even [OK]

Hint: Use n % 2 == 0 to check even numbers [OK]

Common Mistakes:

• Using division instead of modulo
• Returning remainder instead of boolean
• Confusing condition for even check