Parameters and arguments in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a parameter in a Python function?

A parameter is a named variable in a function definition that acts as a placeholder for the value that will be passed to the function when it is called.

beginner

What is an argument in Python?

An argument is the actual value or data you provide to a function when you call it. It fills the parameter's placeholder.

beginner

Explain the difference between parameters and arguments with an example.

In def greet(name):, name is a parameter. When you call greet('Alice'), 'Alice' is the argument passed to the parameter name.

intermediate

What happens if you call a function without providing an argument for a parameter that has no default value?

Python will raise a TypeError because the function expects an argument for that parameter but none was given.

intermediate

What are default parameters in Python functions?

Default parameters are parameters that have a default value assigned in the function definition. If no argument is provided for them, the default value is used.

In the function definition def add(x, y):, what are x and y?

A Parameters

B Arguments

C Functions

D Variables outside the function

x and y are parameters because they are placeholders in the function definition.

What is the argument in the call add(3, 5)?

A x and y

B add

C 3 and 5

D Function name

The values 3 and 5 are arguments passed to the function.

What error occurs if you call greet(name) without an argument?

A SyntaxError

B ValueError

C NameError

D TypeError

A TypeError occurs because the required argument is missing.

Which of these is a correct way to define a default parameter?

A def greet('Friend' = name):

B def greet(name='Friend'):

C def greet(name): name='Friend'

D def greet(name): return 'Friend'

Default parameters are set in the function definition like name='Friend'.

If a function has parameters a, b=2, what happens when you call it with func(5)?

A a=5 and b=2 (default used)

B a=2 and b=5

C Error because b is missing

D Both a and b are 5

Parameter b uses its default value 2 when no argument is given.

Explain in your own words the difference between parameters and arguments in Python functions.

Think about how you prepare a recipe (parameters) and how you actually cook with ingredients (arguments).

Describe what happens if you call a function without providing all required arguments.

Imagine forgetting to bring an ingredient to cook a recipe.

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