Comments in Python - Step-by-Step Execution

Concept Flow - Comments in Python

Start of code

↓

Read line

↓

Is line a comment?

Yes→Ignore line, no action

No↓

Execute line

↓

More lines?

Yes→Read next line

No↓

End of code

Python reads each line. If it sees a comment (starting with #), it skips it and does not run it. Otherwise, it runs the line.

Execution Sample

Python

# This is a comment
print('Hello')  # This prints Hello
# Another comment

This code shows comments ignored and a print statement executed.

Execution Table

Step	Line Read	Is Comment?	Action	Output
1	# This is a comment	Yes	Ignore line
2	print('Hello') # This prints Hello	No	Execute print	Hello
3	# Another comment	Yes	Ignore line

💡 All lines processed; comments ignored, print executed once.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Output	""	""	"Hello"	"Hello"	"Hello"

Key Moments - 2 Insights

Why doesn't the comment line produce any output?

Because the execution_table shows that comment lines are detected and ignored, so no action or output happens for them.

Does a comment after code on the same line affect the code?

No, as seen in step 2, the code before the # runs normally, and the comment after # is ignored.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 1?

A The comment line is ignored

B The comment line is executed

C The print function runs

D An error occurs

💡 Hint

Check the 'Is Comment?' and 'Action' columns for step 1 in the execution_table.

At which step does the program print 'Hello'?

A Step 1

B Step 3

C Step 2

D No step prints 'Hello'

💡 Hint

Look at the 'Output' column in the execution_table for each step.

If we remove the # from the first line, what changes in the execution_table?

A Step 1 will still be ignored

B Step 1 will execute code instead of ignoring

C Step 2 will not run

D No change at all

💡 Hint

Removing # means the line is no longer a comment, so check the 'Is Comment?' and 'Action' columns.

Concept Snapshot

Comments in Python start with # and are ignored by the computer.
They can be on their own line or after code.
Comments help explain code but do not run.
Use # to add notes without affecting program output.

Full Transcript

Python reads code line by line. When it sees a line starting with #, it treats it as a comment and skips running it. Comments can also appear after code on the same line; everything after # is ignored. Only lines without # at the start are executed. In the example, two comment lines are ignored, and one print statement runs, showing 'Hello'. This helps programmers add notes without changing how the program works.