2.2. Syntax Comments

2.2.1. Summary

  • Line comments

  • Multiline comments

  • Inline comments

Line comment:

>>> # good

Multiline comment:

>>> # good 1
>>> # good 2
>>> # good 3

Inline comment:

>>> x = 1  # good

2.2.2. Line Comments

  • PEP 8 -- Style Guide for Python Code

  • For line comments: Hash (#), space and then comment

>>> # my comment

2.2.3. Multiline Comments

  • There are no multiline comments in Python

  • You can create many one line comments

  • All of them will be ignored

>>> # my comment 1
>>> # my comment 2
>>> # my comment 3

2.2.4. Inline Comments

  • PEP 8 -- Style Guide for Python Code

  • For inline comments add two spaces before #

>>> x = 1  # my comment

2.2.5. Convention

  • By convention for inline comments there should be two spaces before #

  • By convention for any comment after # there should be a space

  • Instead of comments write more readable code, which will be self-explanatory

  • Never commit commented out code, use Version Control System instead - e.g.: git blame

Line comment:

>>> # good

>>> #bad

Multiline comment:

>>> # good 1
>>> # good 2
>>> # good 3

>>> #bad 1
>>> #bad 2
>>> #bad 3

Inline comment:

>>> x = 1  # good

>>> x = 1  #bad
>>> x = 1 # bad
>>> x = 1# bad
>>> x = 1 #bad
>>> x = 1#bad

2.2.6. Docstring

  • PEP 257 -- Docstring Conventions

  • Docstring is a first multiline comment in: file/module, class, method/function

  • Used for doctest

  • For multiline str always use three double quote (""") characters

People sometimes use multiline strings to achieve similar behavior as multiline-comment. Unfortunately this requires Python to define string, store it into the memory, and then remove it.

>>> 
... """
... my comment 1
... my comment 2
... my comment 3
... """

2.2.7. Recap

  • Line comments

  • Multiline comments

  • Inline comments

  • After # rest of the line will be ignored

  • By convention for inline comments there should be two spaces before #

  • By convention for any comment after # there should be a space

  • Instead of comments write more readable code, which will be self-explanatory

  • Never commit commented out code, use Version Control System instead - e.g.: git blame

  • IDE has Local history (modifications) and you can compare file

Line comment:

>>> # good

Multiline comment:

>>> # good 1
>>> # good 2
>>> # good 3

Inline comment:

>>> x = 1  # good

2.2.8. Assignments

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% About
# - Name: Syntax Comments Line
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% English
# 1. Add line comment: My comment
# 2. Remember to add space after `#` character
# 3. Run doctests - all must succeed

# %% Polish
# 1. Dodaj komentarz liniowy: My comment
# 2. Pamiętaj o dodaniu spacji po znaku `#`
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Tests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> result = open(__file__).read()
>>> comment = '#' + ' ' + 'My comment'

>>> assert comment in result, \
'Please write proper line comment'
"""

# Add line comment: My comment
# Remember to add space after `#` character



# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% About
# - Name: Syntax Comments Multiline
# - Difficulty: easy
# - Lines: 3
# - Minutes: 2

# %% English
# 1. Add multiline comment:
#    - first line: My comment 1
#    - second line: My comment 2
#    - third line: My comment 3
# 2. Remember to add space after `#` character
# 3. Run doctests - all must succeed

# %% Polish
# 1. Dodaj komentarz wieloliniowy:
#    - pierwsza linia: My comment 1
#    - druga linia: My comment 2
#    - trzecia linia: My comment 3
# 2. Pamiętaj o dodaniu spacji po znaku `#`
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - Each line of a multiline comment should start with `# ` characters

# %% Tests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> result = open(__file__).read()
>>> comment = '\\n'.join([
...     '#' + ' ' + 'My comment 1',
...     '#' + ' ' + 'My comment 2',
...     '#' + ' ' + 'My comment 3',
... ])

>>> assert comment in result, \
'Please write proper multiline comment'
"""

# Add multiline comment:
# - first line: My comment 1
# - second line: My comment 2
# - third line: My comment 3
# Remember to add space after `#` character



# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% About
# - Name: Syntax Comments Inline
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% English
# 1. Add inline comment to `DATA` variable definition
#    with content: My comment
# 2. Remember to add space after `#` character
# 3. Remember to add two spaces before `#` character
# 4. Run doctests - all must succeed

# %% Polish
# 1. Dodaj komentarz na końcu linii do definicji zmiennej `DATA`
#    z treścią: My comment
# 2. Pamiętaj o dodaniu spacji po znaku `#`
# 3. Pamiętaj o dodaniu dwóch spacji przed znakiem `#`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Tests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> result = open(__file__).read()
>>> comment = '  ' + '#' + ' ' + 'My comment'

>>> assert DATA == 1, \
'Do not change the value of the `DATA` variable.'

>>> assert comment in result, \
'Please write proper inline comment'
"""

# Add inline comment to `DATA` variable definition
# with content: My comment
# Remember to add space after `#` character
# Remember to add two spaces before `#` character

DATA = 1