CodeBlanks Logo Icon CodeBlanks
Login Register

Comments

Learn single-line (#) and multi-line (triple-quote) comments.

Why write comments?

Comments are text that Python ignores but explains the code to humans. Comments help you remember what code does later and help others understand it.

A single-line comment starts with the # sign. Everything from # to the end of the line is a comment:

# This is a comment
print("Hello")

Comments support code, they do not replace it. Clear variable names cannot replace a comment, but a good comment always helps.

Multi-line comments

Python has no separate syntax for multi-line comments. Instead we put # at the start of each line, or we use a triple-quoted string:

# This comment spans
# multiple lines

A triple-quoted string is actually a string; but when it is not assigned to a variable, Python ignores it. So it is used for documentation:

"""This is a
doc string"""

The docstring is the topic of a later lesson.

Practice Add a comment

Print Welcome to the screen with print. Add a # Greeting message comment above it.

Starter code

main.py
# Add a comment

Sample solution

main.py
# Greeting message
print("Welcome")

Expected output

Welcome

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Complete the comment line

Question 
# This line is a ____ line
Answer 
# This line is a comment line

Explanation: A line starting with # is a comment.

2 Which of these is a valid Python comment?

  • <!-- Comment -->
  • // User input
  • # User input Correct answer
  • /* Comment */

Explanation: A Python single-line comment starts with #.

3 Match each item to its purpose

Term Meaning
# Single-line comment
""" Triple-quoted string
exit() REPL exit
python3 Start the REPL

All lessons in Beginner

1 Python basics

  1. What is Python?
  2. REPL and print
  3. Comments
  4. Indentation blocks
  5. python -c and scripts
  6. Summary - Python basics

2 Variables

  1. Variable assignment
  2. Multiple assignment
  3. Naming variables
  4. id and type
  5. Swapping variables
  6. Summary - Variables

3 Data types

  1. int and float
  2. bool
  3. str basics
  4. None
  5. Type conversion
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Membership and identity
  6. Summary - Operators

6 String basics

  1. f-string
  2. Concatenation
  3. str.format
  4. Raw strings
  5. Triple-quote
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. elif and else
  3. Nested if
  4. Truthiness
  5. Conditional expression
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. range
  3. The while loop
  4. break and continue
  5. Loop else
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Lists

  1. Declaring lists
  2. Index and slice
  3. List methods
  4. in and count
  5. Sorting lists
  6. Summary - Lists

11 List comprehension

  1. Comprehension basics
  2. Filtered comprehension
  3. Dict and set comprehension
  4. Nested comprehension
  5. Generator expression
  6. Summary - List comprehension

12 Tuple, set and dict

  1. Tuple
  2. Set
  3. Dict basics
  4. Dict methods
  5. Dict comprehension
  6. Summary - Tuple, set and dict

13 Functions

  1. def
  2. return
  3. Docstring
  4. Default parameters
  5. *args and **kwargs
  6. Summary - Functions

14 Function parameters

  1. Positional parameters
  2. Keyword parameters
  3. Keyword-only
  4. Positional-only
  5. Type hints basics
  6. Summary - Function parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string methods

  1. split and join
  2. strip, lstrip, rstrip
  3. replace
  4. find and index
  5. startswith, endswith
  6. Summary - Advanced strings

17 Input and output

  1. input()
  2. int/float conversion
  3. print parameters
  4. f-string formatting
  5. sys.argv
  6. Summary - Input and output

18 Error handling

  1. try/except
  2. else and finally
  3. raise
  4. Exception hierarchy
  5. Custom exceptions
  6. Summary - Error handling

19 Modules

  1. import
  2. from import
  3. as alias
  4. __name__ == '__main__'
  5. Standard library
  6. Summary - Modules

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together