Parameters and arguments in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of 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 TypeError: greet() missing 1 required positional argument: 'greeting'

B Hello, Alice!\nHello, Bob!

C Hi, Alice!\nHi, Bob!

D Hello, Alice!\nHi, Bob!

💡 Hint

Remember the default value is used if no argument is given for that parameter.

The function greet has a default value for greeting. When called with only one argument, greeting uses its default 'Hello'. When called with greeting='Hi', it uses the provided value.

❓ Predict Output

intermediate

Output with *args and **kwargs parameters

What will this code print?

Python

def show_args(*args, **kwargs):
    print(f"Positional: {args}")
    print(f"Keyword: {kwargs}")

show_args(1, 2, a=3, b=4)

A Positional: [1, 2]\nKeyword: {'a': 3, 'b': 4}

B Positional: (1, 2)\nKeyword: {'a': 3, 'b': 4}

C Positional: (1, 2)\nKeyword: [('a', 3), ('b', 4)]

D TypeError: show_args() got multiple values for argument 'a'

💡 Hint

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

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

❓ Predict Output

advanced

Output of function with mutable default argument

What is the output of this code?

Python

def add_item(item, item_list=[]):
    item_list.append(item)
    return item_list

print(add_item('apple'))
print(add_item('banana'))

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

B ['apple']\n['apple']

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

D TypeError: unhashable type: 'list'

💡 Hint

Default arguments are evaluated once when the function is defined, not each time it is called.

The default list is shared across calls, so the second call appends 'banana' to the same list that already contains 'apple'.

❓ Predict Output

advanced

Output of function with positional-only and keyword-only parameters

What will this code print?

Python

def func(a, /, b, *, c):
    return a + b + c

print(func(1, 2, c=3))

A 6

B TypeError: func() missing 1 required keyword-only argument: 'c'

C TypeError: func() got some positional-only arguments passed as keyword arguments

D TypeError: func() missing 1 required positional argument: 'b'

💡 Hint

Parameters before / are positional-only, parameters after * are keyword-only.

Parameter 'a' is positional-only, so it must be passed positionally. 'b' is positional or keyword, 'c' is keyword-only. The call matches these rules.

🧠 Conceptual

expert

Identify the error in function call with argument unpacking

Given the function definition below, which option will cause a TypeError when called?

Python

def combine(a, b, c):
    return a + b + c

A

kwargs = {'a': 1, 'b': 2, 'c': 3}
combine(**kwargs, c=4)

B

args = (1, 2, 3)
combine(*args)

C

kwargs = {'a': 1, 'b': 2}
combine(**kwargs, c=3)

D

args = (1, 2)
combine(*args, 3)

💡 Hint

Check if any argument is passed twice due to unpacking and explicit argument.

Option A passes 'c' twice: once in kwargs and once explicitly, causing TypeError: multiple values for argument 'c'.

Practice

1. What is the role of parameters in a Python function?

easy

A. They are variables defined outside the function.

B. They are placeholders to receive values when the function is called.

C. They are the actual values passed to the function.

D. They are the output values returned by the function.

Solution

1. Step 1: Understand what parameters are

   Parameters are names used in the function definition to hold values passed in.

2. Step 2: Differentiate parameters from arguments

   Arguments are the actual values given when calling the function, parameters receive them.

3. Final Answer:

   They are placeholders to receive values when the function is called. -> Option B

4. Quick Check:

   Parameters = placeholders [OK]

Hint: Parameters are names in function definition, not actual values. [OK]

Common Mistakes:

• Confusing parameters with arguments
• Thinking parameters are outputs
• Mixing parameters with global variables

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

easy

A. function my_func(a, b):

B. def my_func[a, b]:

C. def my_func(a, b):

D. def my_func(a b):

Solution

1. Step 1: Recall Python function syntax

   Functions are defined using def keyword, parameters inside parentheses separated by commas.

2. Step 2: Check each option

   def my_func(a, b): uses correct syntax: def my_func(a, b):. Others have syntax errors.

3. Final Answer:

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

4. Quick Check:

   def + (params separated by commas) = correct [OK]

Hint: Use def and parentheses with commas for parameters. [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Omitting commas between parameters
• Using wrong keywords like 'function'

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

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

print(greet("Alice"))

medium

A. Hello, Alice!

B. Hello, name!

C. greet(Alice)

D. Error: name not defined

Solution

1. Step 1: Understand the function call

   The function greet takes one parameter name and returns a greeting string with that name.

2. Step 2: Substitute the argument value

   Calling greet("Alice") passes "Alice" as the argument, so the returned string is "Hello, Alice!".

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Argument replaces parameter in output [OK]

Hint: Arguments fill parameters; output shows argument value. [OK]

Common Mistakes:

• Printing parameter name instead of argument value
• Confusing function name with output
• Expecting error due to missing quotes

4. Identify the error in this function call:

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

result = add(5)

medium

A. Missing one argument in the function call.

B. Function name is incorrect.

C. Parameters should be strings.

D. No error, code runs fine.

Solution

1. Step 1: Check function definition

   The function add requires two parameters: x and y.

2. Step 2: Check function call arguments

   The call add(5) provides only one argument, missing the second one.

3. Final Answer:

   Missing one argument in the function call. -> Option A

4. Quick Check:

   Parameters count must match arguments count [OK]

Hint: Count parameters and arguments; they must match. [OK]

Common Mistakes:

• Assuming missing arguments default to zero
• Thinking function name is wrong
• Ignoring argument count mismatch

5. Consider this function:

def multiply(a, b=2):
    return a * b

print(multiply(4))
print(multiply(4, 3))

What will be the output and why?

hard

A. Error; cannot mix default and non-default parameters.

B. 6 and 12; default parameter is ignored.

C. 8 and 8; default parameter always used.

D. 8 and 12; second argument overrides default parameter.

Solution

1. Step 1: Understand default parameters

   Parameter b has a default value 2, used if no argument is given.

2. Step 2: Analyze each function call

   First call multiply(4) uses default b=2, so 4*2=8.
   Second call multiply(4, 3) overrides default with 3, so 4*3=12.

3. Final Answer:

   8 and 12; second argument overrides default parameter. -> Option D

4. Quick Check:

   Default parameters used unless overridden [OK]

Hint: Default parameters fill missing arguments; explicit arguments override. [OK]

Common Mistakes:

• Thinking default parameters are always used
• Believing mixing default and non-default causes error
• Ignoring argument overriding default