Python Program to Count Words in String

You can count words in a string in Python by using len(string.split()), which splits the string by spaces and counts the resulting parts.

Examples

InputHello world

Output2

InputPython programming is fun

Output4

Input

Output0

How to Think About It

To count words in a string, think of words as groups of characters separated by spaces. Splitting the string by spaces creates a list of words, and counting the list's length gives the number of words.

Algorithm

1

Get the input string

2

Split the string into parts using spaces as separators

3

Count how many parts are in the list

4

Return or print the count

Code

python

text = input("Enter a string: ")
words = text.split()
count = len(words)
print("Number of words:", count)

Output

Enter a string: Hello world
Number of words: 2

Dry Run

Let's trace the input 'Hello world' through the code

1

Input string

text = 'Hello world'

2

Split string

words = ['Hello', 'world']

3

Count words

count = 2

4

Print result

Output: Number of words: 2

Step	Words List	Count
Split string	['Hello', 'world']	2

Why This Works

Step 1: Splitting the string

The split() method breaks the string into a list of words separated by spaces.

Step 2: Counting words

Using len() on the list gives the total number of words.

Step 3: Printing the result

The program prints the count so the user can see how many words were in the input.

Alternative Approaches

Using a loop to count words

python

text = input("Enter a string: ")
count = 0
for word in text.split():
    count += 1
print("Number of words:", count)

This method manually counts words by looping, which is more verbose but shows the counting process clearly.

Using regular expressions

python

import re
text = input("Enter a string: ")
words = re.findall(r'\b\w+\b', text)
print("Number of words:", len(words))

This method counts words more precisely by matching word patterns, useful if input has punctuation.

Complexity: O(n) time, O(n) space

Time Complexity

Splitting the string scans each character once, so time grows linearly with input size.

Space Complexity

The split method creates a list of words, so extra space grows with the number of words.

Which Approach is Fastest?

Using split() and len() is fastest and simplest for most cases; regex is slower but more precise.

Approach	Time	Space	Best For
split() and len()	O(n)	O(n)	Simple word counts
Loop counting	O(n)	O(n)	Learning counting process
Regex findall	O(n)	O(n)	Handling punctuation accurately