Variable-length arguments (*args) in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does *args mean in a Python function?

*args allows a function to accept any number of positional arguments as a tuple.

beginner

How do you access the third argument passed using *args?

You access it like a tuple element: args[2] (index starts at 0).

beginner

Can a function have both regular parameters and *args?

Yes, regular parameters come first, then *args to catch extra positional arguments.

beginner

What type is args inside the function when using *args?

args is a tuple containing all extra positional arguments passed.

beginner

Write a simple function using *args that prints all arguments.

def print_all(*args): for arg in args: print(arg)

What does *args collect inside a function?

A A dictionary of keyword arguments

B A tuple of extra positional arguments

C A list of all arguments

D A single string argument

*args collects extra positional arguments as a tuple.

How do you define a function that accepts any number of positional arguments?

A def func(args):

B def func(args*):

C def func(**args):

D def func(*args):

Use *args to accept variable positional arguments.

If a function is defined as def f(a, *args):, what happens when you call f(1, 2, 3)?

A Error because of too many arguments

B a=(1, 2, 3), args=empty

C a=1, args=(2, 3)

D a=1, args=2

The first argument goes to a, the rest go into args tuple.

What is the type of args inside the function?

A tuple

B list

C dict

D set

args is always a tuple.

Can *args be used to accept keyword arguments?

A No, <code>**kwargs</code> is for keyword arguments

B Yes, <code>*args</code> accepts keywords

C Only if keywords are strings

D Only if keywords are numbers

*args is for positional arguments; **kwargs is for keyword arguments.

Explain how *args works in a Python function and give an example.

Think about how to catch extra inputs without naming them all.

Describe the difference between regular parameters and *args in function definitions.

Consider how many arguments each can take.

Practice

1. What does *args do in a Python function?

easy

A. Allows the function to accept any number of extra positional arguments

B. Allows the function to accept only keyword arguments

C. Restricts the function to accept exactly one argument

D. Makes the function return multiple values

Solution

1. Step 1: Understand the role of *args

   *args collects extra positional arguments passed to a function into a tuple.

2. Step 2: Compare options with this behavior

   Only Allows the function to accept any number of extra positional arguments correctly describes this behavior; others describe different concepts.

3. Final Answer:

   Allows the function to accept any number of extra positional arguments -> Option A

4. Quick Check:

   *args = flexible positional inputs [OK]

Hint: Remember *args packs extra positions into a tuple [OK]

Common Mistakes:

• Confusing *args with **kwargs
• Thinking *args limits arguments
• Assuming *args returns multiple values

2. Which of the following is the correct syntax to define a function that accepts variable-length positional arguments?

easy

A. def func(args*):

B. def func(*args):

C. def func(**args):

D. def func(args**):

Solution

1. Step 1: Recall the syntax for variable-length positional arguments

   The correct syntax uses an asterisk before the parameter name: *args.

2. Step 2: Match options with correct syntax

   def func(*args): matches the correct syntax; others are invalid or for different purposes.

3. Final Answer:

   def func(*args): -> Option B

4. Quick Check:

   Star before name = variable positional args [OK]

Hint: Use * before parameter name for variable positional args [OK]

Common Mistakes:

• Using **args instead of *args
• Placing * after the parameter name
• Confusing syntax with keyword arguments

3. What is the output of the following code?

def add_numbers(*args):
    return sum(args)

print(add_numbers(1, 2, 3, 4))

medium

A. 10

B. 1234

C. TypeError

D. None

Solution

1. Step 1: Understand how *args works in the function

   The function collects all arguments into a tuple and sums them using sum().

2. Step 2: Calculate the sum of the arguments

   1 + 2 + 3 + 4 = 10, so the function returns 10.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   Sum of (1,2,3,4) = 10 [OK]

Hint: Sum all *args values to get total [OK]

Common Mistakes:

• Concatenating numbers as strings
• Expecting a TypeError for multiple args
• Forgetting that *args is a tuple

4. Identify the error in this function definition:

def greet(*names):
    for name in names
        print(f"Hello, {name}!")

medium

A. print statement syntax error

B. Incorrect use of *args syntax

C. Missing colon after for loop

D. Function cannot have *args

Solution

1. Step 1: Check the for loop syntax

   The for loop line is missing a colon at the end, which is required in Python.

2. Step 2: Verify other parts of the function

   The *names syntax and print statement are correct; the function can have *args.

3. Final Answer:

   Missing colon after for loop -> Option C

4. Quick Check:

   For loops need a colon [:] [OK]

Hint: Check colons after for, if, while statements [OK]

Common Mistakes:

• Forgetting colon after for loop
• Confusing *args with **kwargs
• Incorrect indentation

5. How can you write a function that accepts any number of positional arguments and returns a list of their squares?

hard

A. def squares(args): return [x**2 for x in args]

B. def squares(*args): return x**2 for x in args

C. def squares(**args): return [x**2 for x in args]

D. def squares(*args): return [x**2 for x in args]

Solution

1. Step 1: Use *args to accept variable positional arguments

   The function parameter must be *args to accept any number of positional arguments.

2. Step 2: Return a list of squares using list comprehension

   Use [x**2 for x in args] to square each argument and collect results in a list.

3. Final Answer:

   def squares(*args): return [x**2 for x in args] -> Option D

4. Quick Check:

   Use *args and list comprehension for squares [OK]

Hint: Use *args and list comprehension for flexible squares [OK]

Common Mistakes:

• Using **args instead of *args
• Forgetting to return a list
• Incorrect comprehension syntax