String immutability in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean that strings are immutable in Python?

It means once a string is created, it cannot be changed. Any operation that seems to modify a string actually creates a new string.

beginner

Why can't you change a character in a Python string directly?

Because strings are immutable, their characters cannot be changed one by one. You must create a new string with the desired changes.

intermediate

What happens when you do s = s + 'a' on a string s?

A new string is created by adding 'a' to s, and s now points to this new string. The original string stays unchanged in memory until garbage collected.

intermediate

How does string immutability help with program safety?

Since strings cannot change, they prevent accidental changes and make programs easier to understand and debug.

beginner

Can you modify a string in place in Python? If not, what is the alternative?

No, you cannot modify a string in place. Instead, you create a new string with the changes you want.

What does string immutability mean in Python?

A Strings are only immutable in some cases

B Strings can be changed anytime

C Strings are stored in a mutable list

D Strings cannot be changed after creation

Strings in Python cannot be changed once created; any change creates a new string.

What happens if you try to change a character in a string directly?

A Python raises an error

B The character changes successfully

C The string becomes a list

D The string deletes itself

Python raises a TypeError because strings are immutable and do not support item assignment.

How can you add a character to a string s in Python?

A s = s + 'a'

B s[0] = 'a'

C s.append('a')

D s.insert(0, 'a')

You create a new string by concatenation; s + 'a' returns a new string.

Why is string immutability useful?

A It makes strings slower

B It allows strings to be changed in place

C It prevents accidental changes and bugs

D It uses more memory always

Immutability helps keep data safe and programs easier to understand.

Which of these is NOT true about Python strings?

A They are immutable

B You can change characters directly

C Concatenation creates new strings

D They help with program safety

You cannot change characters directly in a string because strings are immutable.

Explain in your own words what string immutability means and why it matters.

Think about how changing a string is like making a new copy instead of editing the original.

Describe what happens in memory when you do s = s + 'a' with a string s.

Imagine copying a photo and adding a sticker on the copy, not the original.