len() function in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the len() function do in Python?

The len() function returns the number of items in an object like a string, list, tuple, or dictionary.

beginner

How do you use len() with a string?

You pass the string inside the parentheses, like len('hello'), which returns 5 because 'hello' has 5 characters.

beginner

Can len() be used with dictionaries? What does it return?

Yes, len() works with dictionaries and returns the number of key-value pairs in the dictionary.

beginner

What will len([]) return?

It returns 0 because the list is empty and has no items.

beginner

Is it possible to use len() on numbers like len(123)? Why or why not?

No, len() cannot be used on numbers because numbers are not collections or sequences. It only works on objects that contain multiple items.

What does len('Python') return?

A 5

B 6

C 7

D Error

'Python' has 6 characters, so len('Python') returns 6.

What will len([1, 2, 3, 4]) return?

A 4

B 3

C 5

D Error

The list has 4 items, so len() returns 4.

Which of these can len() be used on?

A Strings

B Integer numbers

C Floating point numbers

D None of the above

len() works on strings because they are sequences of characters.

What does len({'a':1, 'b':2, 'c':3}) return?

A 2

B 6

C Error

D 3

The dictionary has 3 key-value pairs, so len() returns 3.

What happens if you try len(100)?

A Returns 3

B Returns 1

C Raises a TypeError

D Returns 0

Numbers are not collections, so len(100) raises a TypeError.

Explain how the len() function works with different data types in Python.

Think about what kinds of things have a length or count.

Describe a real-life example where you might use the len() function in a program.

Imagine you want to know how many things are inside a box or how long a word is.