Argument order rules in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function call with mixed arguments

What is the output of this Python code?

Python

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

print(greet("Alice", punctuation="."))

A TypeError: positional argument follows keyword argument

B Hello, Alice!

C Hello, Alice.

D Hello, punctuation=., Alice

💡 Hint

Remember that positional arguments come before keyword arguments.

The function call uses a positional argument for 'name' and a keyword argument for 'punctuation'. The default greeting 'Hello' is used. So the output is 'Hello, Alice.'.

❓ Predict Output

intermediate

Error from wrong argument order

What error does this code produce?

Python

def add(x, y=5, z):
    return x + y + z

add(1, 2, 3)

A 6

B NameError: name 'z' is not defined

C SyntaxError: invalid syntax

D SyntaxError: non-default argument follows default argument

💡 Hint

Check the order of parameters with and without default values.

In Python, parameters with default values must come after parameters without defaults. Here, 'z' has no default but comes after 'y' which has a default, causing a SyntaxError.

❓ Predict Output

advanced

Output with *args and keyword-only arguments

What is the output of this code?

Python

def func(a, b, *args, c=10, d=20):
    return a + b + sum(args) + c + d

print(func(1, 2, 3, 4, c=5))

A 35

B 40

C TypeError: func() missing 1 required keyword-only argument: 'd'

D 30

💡 Hint

Remember that after *args, parameters are keyword-only.

Arguments: a=1, b=2, args=(3,4), c=5 (keyword), d=20 (default). Sum is 1+2+3+4+5+20=35.

❓ Predict Output

advanced

Output with positional-only and keyword-only arguments

What is the output of this code?

Python

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

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

A 6

B TypeError: example() missing 1 required positional argument: 'b'

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

D 5

💡 Hint

Positional-only arguments must be passed positionally, keyword-only must be passed by name.

a=1 (positional-only), b=2 (positional or keyword), c=3 (keyword-only). Sum is 1+2+3=6.

🧠 Conceptual

expert

Identify the invalid function definition

Which of these function definitions is invalid due to argument order rules?

A def f(a, b=2, *, c, d=4): pass

B def f(a=1, b, c=3): pass

C def f(a, /, b, *, c=3): pass

D def f(*args, b, c=3): pass

💡 Hint

Parameters with default values must come after those without defaults.

Option B has a parameter 'a' with default before 'b' without default, which is invalid syntax in Python.

Practice

1.

Which of the following correctly describes the order of arguments in a Python function definition?

easy

A. Positional-only, positional-or-keyword, keyword-only

B. Keyword-only, positional-only, positional-or-keyword

C. Positional-or-keyword, keyword-only, positional-only

D. Positional-or-keyword, positional-only, keyword-only

Solution

1. Step 1: Recall argument order rules

   Python functions must define arguments in the order: positional-only, positional-or-keyword, then keyword-only.

2. Step 2: Match the correct order

   Positional-only, positional-or-keyword, keyword-only matches this exact order, others do not.

3. Final Answer:

   Positional-only, positional-or-keyword, keyword-only -> Option A

4. Quick Check:

   Argument order = Positional-only, positional-or-keyword, keyword-only [OK]

Hint: Remember: positional-only first, then normal, then keyword-only [OK]

Common Mistakes:

• Confusing keyword-only and positional-only order
• Thinking positional-or-keyword comes first
• Ignoring positional-only arguments

2.

Which of the following function definitions is syntactically correct in Python?

def example(a, /, b, *, c):
    pass

easy

A. def example(a, /, b, *, c): pass

B. def example(a, b, *, /, c): pass

C. def example(a, *, b, /, c): pass

D. def example(/, a, b, *, c): pass

Solution

1. Step 1: Understand syntax for positional-only and keyword-only

   The slash (/) marks positional-only arguments before it, and the asterisk (*) marks keyword-only arguments after it.

2. Step 2: Check each option's order

   def example(a, /, b, *, c): pass correctly places a before / (positional-only), b as positional-or-keyword, and c after * (keyword-only). Others have invalid order or misplaced / and *.

3. Final Answer:

   def example(a, /, b, *, c): pass -> Option A

4. Quick Check:

   Syntax with / and * correct = def example(a, /, b, *, c): pass [OK]

Hint: Slash (/) before positional-only, star (*) before keyword-only [OK]

Common Mistakes:

• Placing / after positional-or-keyword arguments
• Putting * before /
• Using / as a standalone argument

3.

What is the output of this code?

def func(a, /, b, *, c):
    print(a, b, c)

func(1, 2, c=3)

medium

A. TypeError: missing required keyword-only argument 'c'

B. 1 2 3

C. TypeError: positional argument after keyword argument

D. SyntaxError

Solution

1. Step 1: Understand argument passing

   a is positional-only, so must be passed by position (1). b is positional-or-keyword, passed by position (2). c is keyword-only, passed as c=3.

2. Step 2: Check function call validity and output

   All arguments are passed correctly. The print outputs the values: 1 2 3.

3. Final Answer:

   1 2 3 -> Option B

4. Quick Check:

   func(1, 2, c=3) prints 1 2 3 [OK]

Hint: Positional-only args by position, keyword-only by name [OK]

Common Mistakes:

• Passing positional-only argument by keyword
• Passing keyword-only argument positionally
• Confusing argument order in call

4.

Identify the error in this function call:

def f(x, /, y, *, z):
    return x + y + z

f(x=1, y=2, z=3)

medium

A. No error, returns 6

B. TypeError: missing required positional argument y

C. SyntaxError: invalid function call

D. TypeError: x is positional-only and cannot be passed as keyword

Solution

1. Step 1: Check argument types in definition

   x is positional-only (before /), y is positional-or-keyword, z is keyword-only (after *).

2. Step 2: Analyze function call

   Calling f(x=1, y=2, z=3) tries to pass x by keyword, which is not allowed for positional-only arguments, causing a TypeError.

3. Final Answer:

   TypeError: x is positional-only and cannot be passed as keyword -> Option D

4. Quick Check:

   Positional-only args cannot be keyword = TypeError [OK]

Hint: Positional-only args can't be named in calls [OK]

Common Mistakes:

• Passing positional-only argument by keyword
• Thinking all arguments can be named
• Ignoring the / marker meaning

5.

You want to define a function that takes exactly two positional-only arguments, one positional-or-keyword argument, and two keyword-only arguments. Which of these definitions is correct?

1. def func(a, b, /, c, *, d, e): pass
2. def func(a, /, b, c, *, d, e): pass
3. def func(a, b, c, /, *, d, e): pass
4. def func(a, b, /, *, c, d, e): pass

hard

A. Definition 3

B. Definition 2

C. Definition 1

D. Definition 4

Solution

1. Step 1: Identify argument categories

   Two positional-only args: before / (a, b). One positional-or-keyword: after / and before * (c). Two keyword-only: after * (d, e).

2. Step 2: Check each definition

   Definition 1 matches this order exactly: a, b before /, c after /, d, e after *. Others have wrong placement of / or * or argument counts.

3. Final Answer:

   Definition 1 -> Option C

4. Quick Check:

   Two positional-only, one normal, two keyword-only = Definition 1 [OK]

Hint: Two positional-only before /, one normal after, two keyword-only after * [OK]

Common Mistakes:

• Placing too many args before or after / or *
• Miscounting positional-only arguments
• Confusing keyword-only with positional-or-keyword