Why exceptions occur in Python - Visual Breakdown

Concept Flow - Why exceptions occur

Start Program

↓

Execute Code

↓

Error Occurs?

No→Continue Execution

Yes↓

Raise Exception

↓

Handle Exception?

No→Program Stops

Yes↓

Run Exception Handler

↓

Continue or Stop

The program runs code, if an error happens, an exception is raised. If handled, the program continues; if not, it stops.

Execution Sample

Python

x = 10
print(x / 2)
print(x / 0)
print("End")

This code divides 10 by 2, then tries to divide by zero causing an exception, stopping the program before printing "End".

Execution Table

Step	Code Line	Action	Result	Exception Raised?
1	x = 10	Assign 10 to x	x=10	No
2	print(x / 2)	Calculate 10 / 2 and print	Prints 5.0	No
3	print(x / 0)	Calculate 10 / 0	Error: division by zero	Yes
4	print("End")	Not executed	No output	No

💡 Exception raised at step 3 stops program before step 4

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
x	undefined	10	10	10	10

Key Moments - 2 Insights

Why does the program stop after the division by zero?

Because at step 3 in the execution_table, an exception is raised and not handled, so the program stops immediately without running step 4.

Why is the variable x still 10 after the exception?

The exception happens during calculation, not assignment, so x remains unchanged as shown in variable_tracker after step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is printed at step 2?

A Error

B 5.0

C 10

D Nothing

💡 Hint

Check the 'Result' column for step 2 in the execution_table.

At which step does the exception occur?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Exception Raised?' column in the execution_table.

If we handled the exception at step 3, what would happen to step 4?

A It would run and print "End"

B It would still not run

C The program would crash earlier

D Step 4 would print an error

💡 Hint

Handling exceptions allows the program to continue after the error, so step 4 would execute.

Concept Snapshot

Why exceptions occur:
- Exceptions happen when code runs into an error (like dividing by zero).
- When an exception occurs, Python stops normal execution.
- If the exception is not handled, the program stops.
- Handling exceptions lets the program continue safely.
- Always expect and handle possible errors in your code.

Full Transcript

This visual trace shows why exceptions occur in Python. The program starts by assigning 10 to x, then prints 10 divided by 2, which works fine. Next, it tries to divide 10 by zero, which causes an exception. Because this exception is not handled, the program stops immediately and does not print "End". The variable x remains 10 throughout because the error happens during calculation, not assignment. Understanding this flow helps beginners see how errors stop programs and why handling exceptions is important.