Assert statement usage in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the assert statement in Python?

The assert statement checks if a condition is true. If it is false, it stops the program and raises an AssertionError. It helps catch bugs early by verifying assumptions.

beginner

How do you write an assert statement with a custom error message?

Use assert condition, 'error message'. If the condition is false, Python shows the message with the AssertionError.

beginner

What happens when an assert statement fails?

Python raises an AssertionError and stops running the program unless the error is caught by a try-except block.

intermediate

Can assert statements be disabled? If yes, how?

Yes, running Python with the -O (optimize) flag disables assert statements, so they do not run and do not check conditions.

intermediate

Is it good practice to use assert for data validation in production code?

No, assert is mainly for debugging and testing. For production, use proper error handling because assert can be disabled.

What does this code do? <br>

assert 5 > 3

A Ignores the statement

B Raises an error because 5 is not greater than 3

C Prints 5 and 3

D Checks if 5 is greater than 3 and continues if true

The assert checks if 5 > 3, which is true, so the program continues without error.

What error is raised when an assert condition fails?

A ValueError

B TypeError

C AssertionError

D RuntimeError

When an assert condition is false, Python raises an AssertionError.

How can you disable assert statements in Python?

A Run Python with the -O flag

B Set a global variable

C Use a try-except block

D You cannot disable assert statements

Running Python with the -O (optimize) flag disables assert statements.

Which is the correct way to add a message to an assert?

A assert condition : 'message'

B assert condition, 'message'

C assert(condition, 'message')

D assert 'message' if condition

The syntax is assert condition, 'message' to show a custom error message.

Should assert be used for checking user input in production?

A No, use proper error handling

B Yes, always

C Only for numbers

D Only if input is from a file

Assert is for debugging, not for production input validation.

Explain how the assert statement works and when it should be used.

Think about how assert helps catch mistakes early.

Describe how to write an assert statement with a custom error message and why that might be helpful.

Custom messages make errors clearer.