Lesson 6

Comments - notes for people

After this lesson: You'll add comments that Python skips to your code and learn to switch lines off with #.

Video

The video for this lesson is coming soon.

Explanation

Sometimes you want to leave a note in your code - for yourself or for a friend: what does this line do? Today you'll meet comments - text that Python simply skips. 📝

Comments - notes for people

A line that starts with # is a comment. Python skips it - it doesn't run it and prints nothing. Comments are notes for you or for a friend reading your code:

# Prints the match score
print("FC Bajtek", 3, "-", 1, "FC Python")

A comment can also go at the end of a line of code - everything from # to the end of the line is skipped.

Bajtek and the notes in the code 🎬

Click Next to go step by step.

Bajtek

What does this do?😕

📄code without notes➡️🤔

Code

print("FC Bajtek", 3, "-", 1, "FC Python")

🖥️ Screen

Kuba doesn't get it

Bajtek wrote a program about a match. Kuba looks at the code and scratches his head: what does this line do? Code is for the computer - it's not always easy for a person to understand.

Step 1 / 6

Python skips comments

See that the arrow skips the comment lines - nothing is printed.

Code

1# This is a comment
2print("Hello")
3# This one too
4print("Python")  # a comment at the end of the line

Screen

▍

1/3 · line 2 runs next

Comments in the middle of a program

Lines with # print nothing - the arrow just skips them.

Code

1# This is a note for people
2print("One")
3# print("This won't appear")
4print("Two")  # a note at the end

Screen

▍

1/3 · line 2 runs next

A smiley with instructions 🙂

The comments say what each part does. The screen shows only the picture.

Code

1# eyes
2print(" o   o")
3# nose
4print("   ^")
5# smile
6print("  ---")

Screen

▍

1/4 · line 2 runs next

Switching lines off

A # at the start "switches off" a line. Remove it and the line works again.

Code

1print("On")
2# print("Off")
3print("Also on")

Screen

▍

1/3 · line 1 runs next

# in quotes is not a comment

Watch out, a trap! The # sign starts a comment only outside quotes. Inside quotes it's an ordinary character, like a letter:

print("Bajtek #1")

prints Bajtek #1 - with the hash.

A hash inside text and outside it

The first # is in quotes - it gets printed. The second # is outside the quotes - it starts a comment, so the text after it disappears.

Code

1print("Bajtek #1")
2print("Bajtek")  # 1

Screen

▍

1/3 · line 1 runs next

What does the program print?

print("Bajtek #2")  # super

What are comments for?

to describe what a piece of code does - in a week you'll forget yourself!
to switch off a line for a moment without deleting it.

The judge only sees what the program prints - comments don't change the result.

Remember

# starts a comment - Python skips everything from # to the end of the line.
A comment can be on its own line or at the end of a line of code.
# in quotes is an ordinary character, not a comment.

Great! Now the tasks: add comments and switch off the lines you don't need. 📝

Tasks from the video

We solve them together in the video - pause it and try first on your own.

1A comment 2Start and stop 3A comment at the end of a line 4Switch off a line 5Switch off two lines 6A hash inside text 7A described kitten 8Switch off the wrong operation 9Hide the broken line 10A note next to a division

Practice tasks

Try to solve them without the video. Stuck? Every task has hints and an editorial.

11Hidden comments 12A house with comments 13Every other line 14A question in a comment 15Weeks and days