How to Build a Text Processor in Python

This code defines functions to count words, sentences, and find the longest word in a text, then prints basic statistics like uppercase and lowercase versions.

Easy Python 3.9+ Aug 9, 2026 Strings & text 15 views 0 copies

text-processing strings word-count sentence-count

Python code

32 lines

Python 3.9+

def count_words(text):
    return len(text.split())


def count_sentences(text):
    sentence_endings = ".!?"
    count = 0
    for char in text:
        if char in sentence_endings:
            count += 1
    return count


def longest_word(text):
    words = text.split()
    if not words:
        return ""
    return max(words, key=len)


def process_text(text):
    print(f"Original text: {text}")
    print(f"Word count: {count_words(text)}")
    print(f"Sentence count: {count_sentences(text)}")
    print(f"Longest word: {longest_word(text)}")
    print(f"Uppercase: {text.upper()}")
    print(f"Lowercase: {text.lower()}")


if __name__ == "__main__":
    sample = "Hello world! This is Python. It is fun."
    process_text(sample)

Output

stdout

Original text: Hello world! This is Python. It is fun.
Word count: 7
Sentence count: 3
Longest word: Python
Uppercase: HELLO WORLD! THIS IS PYTHON. IT IS FUN.
Lowercase: hello world! this is python. it is fun.

How it works

The count_words function uses split() which splits on whitespace, so it correctly counts words separated by spaces. count_sentences counts characters that are ., !, or ?; this works for simple cases but assumes sentences end with these punctuation marks. longest_word finds the maximum word based on length using max(key=len). The process_text function prints formatted output, making it easy to see text analysis at a glance.

Common mistakes

Not handling empty text for longest_word, but here it returns an empty string.
Counting decimal points as sentence endings, e.g., in '3.14'.
Assuming each sentence ends with punctuation; missing periods in abbreviations like 'Mr.'.
Using split(',') instead of split() when trying to count words.

Variations

Use regular expressions to count sentences more accurately with `re.split(r'(?<=[.!?])\s+', text)`.
Use `collections.Counter` to get word frequency along with counts.

Real-world use cases

Building a readability analyzer that computes word counts for content marketing reports.
Creating a simple text metrics tool to gauge essay length in educational apps.
Preprocessing user input in search features to extract keywords by length.

How to Build a Text Processor in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Strings & text

Tutorials

Quizzes

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Strings & text

Keep learning

Tutorials

Quizzes