Python Basics — Syntax & Fundamentals Exercises

Practice Exercises — Syntax & Fundamentals

Test your understanding of Python syntax, indentation, keywords, comments, and PEP 8 conventions with these exercises.

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Exercise 1: Fix the Indentation

The following code has indentation errors. Fix them so the code runs correctly.

def greet(name):
print("Hello, " + name + "!")
    if name == "Python":
  print("Welcome back!")

Show Answer

Answer:

def greet(name):
    print("Hello, " + name + "!")
    if name == "Python":
        print("Welcome back!")

Expected output (when called with greet("Python")):

Hello, Python!
Welcome back!

Explanation: Every code block after a colon (:) must be indented by 4 spaces. The print inside def needs 4 spaces, and the print inside if needs 8 spaces (two levels).

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Exercise 2: Identify the Keywords

Look at this code and list all the Python keywords used:

def is_even(number):
    if number % 2 == 0:
        return True
    else:
        return False

for i in range(10):
    if is_even(i) and not i == 0:
        print(i)

Show Answer

Answer: The Python keywords in this code are:

Keyword	Line
def	Line 1
if	Line 2, Line 8
return	Line 3, Line 5
True	Line 3
else	Line 4
False	Line 5
for	Line 7
in	Line 7
and	Line 8
not	Line 8

Total: 10 keywords (with if and return used twice each).

You can verify keywords with:

import keyword
print(keyword.kwlist)

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Exercise 3: Write Proper Comments

Rewrite this code with proper comments and a docstring following best practices:

def f(x, y):
    z = x * y * 0.08
    return x * y + z

Show Answer

Answer:

def calculate_total_with_tax(price, quantity):
    """Calculate the total cost including 8% sales tax.

    Args:
        price: The unit price of the item.
        quantity: The number of items purchased.

    Returns:
        The total cost including tax.
    """
    # Calculate tax at 8% rate
    tax = price * quantity * 0.08

    return price * quantity + tax

Key improvements:

• Descriptive function name (calculate_total_with_tax instead of f)
• Descriptive parameter names (price, quantity instead of x, y)
• Docstring explaining what the function does, its parameters, and return value
• Comment explaining the tax calculation
• Descriptive variable name (tax instead of z)

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Exercise 4: Fix PEP 8 Violations

This code works but has multiple PEP 8 violations. Rewrite it following PEP 8:

import sys,os
import math
from collections import OrderedDict
import json
x=10
y =20
MyList = [1,2,3,4,5]
def Calc( a,b ):
    RESULT=a+b
    return RESULT
class my_class:
    def MyMethod(self):
        pass

Show Answer

Answer:

import json
import math
import os
import sys
from collections import OrderedDict

x = 10
y = 20
my_list = [1, 2, 3, 4, 5]


def calc(a, b):
    result = a + b
    return result


class MyClass:

    def my_method(self):
        pass

Violations fixed:

Issue	Before	After
Multiple imports on one line	import sys,os	Separate lines
Import order	Mixed up	stdlib alphabetically, then from
No spaces around =	x=10	x = 10
No space after commas	[1,2,3]	[1, 2, 3]
Spaces inside parentheses	Calc( a,b )	calc(a, b)
Function name PascalCase	Calc	calc
Variable name PascalCase	MyList	my_list
UPPER_CASE for non-constant	RESULT	result
Class name snake_case	my_class	MyClass
Method name PascalCase	MyMethod	my_method
Missing blank lines	No gaps	2 blank lines before def/class

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Exercise 5: Identify Valid Identifiers

Which of the following are valid Python identifiers? For each invalid one, explain why.

my_variable
2nd_place
_private
class
user-name
__init__
first name
MAX_SIZE
$price
camelCase

Show Answer

Answer:

Identifier	Valid?	Reason
my_variable	✅ Yes	Letters, underscores — valid snake_case
2nd_place	❌ No	Cannot start with a digit
_private	✅ Yes	Leading underscore is valid (convention for private)
class	❌ No	class is a reserved keyword
user-name	❌ No	Hyphens (-) are not allowed in identifiers
__init__	✅ Yes	Double underscore (“dunder”) names are valid
first name	❌ No	Spaces are not allowed in identifiers
MAX_SIZE	✅ Yes	Valid — convention for constants
$price	❌ No	Special characters ($) are not allowed
camelCase	✅ Yes	Technically valid, but PEP 8 prefers snake_case

Rule of thumb: Identifiers can contain letters (a–z, A–Z), digits (0–9), and underscores (_). They must start with a letter or underscore, and cannot be a Python keyword.

Verify a keyword:

import keyword
print(keyword.iskeyword("class"))  # True
print(keyword.iskeyword("my_var")) # False

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Scoring Guide

Score	Level
5/5	Excellent — You’ve mastered Python syntax fundamentals
4/5	Great — Minor gaps, review the topic you missed
3/5	Good — Review PEP 8 conventions and keywords
2/5	Needs Work — Re-read the syntax fundamentals chapter
1/5	Keep Going — Practice more and revisit indentation rules

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Next chapter: Variables & Data Types →