Counting words
Input
len(Sentence("Hello world"))
Output
2
The sentence contains two words: 'Hello' and 'world'.
Full lesson preview
Support len() with __len__
Make a Sentence class compatible with Python's len() by implementing __len__.
Python practice9 minMagic Methods & Operator OverloadingBeginnerLast updated April 11, 2026
Problem statement
Write a class Sentence that accepts a text string. Implement the __len__ magic method so that len(sentence) returns the number of words in the sentence. Words are defined as sequences of non-whitespace characters separated by any whitespace (spaces, tabs, newlines). The class should handle empty strings and strings with extra whitespace correctly.
Task
Implement __len__ for a Sentence class so len(instance) returns the number of words in the sentence.
Examples
Input format
The tests call len(Sentence(text)) where text is a string literal.
Output format
An integer representing the number of words in the sentence.
Constraints
- Use Python's definition of whitespace splitting (str.split()).
- Return 0 for empty or whitespace-only strings.
Samples
Sample 1
Input
len(Sentence(" leading and multiple spaces "))
Output
4
split() ignores extra whitespace and counts 4 words.