Python Program to Reverse Words in a Sentence

Reversing words in a sentence is a common string manipulation problem in Python.

It helps build understanding of string operations, lists, and logic building.

1. Understanding the Problem

Given a sentence, reverse the order of words while keeping words intact.

Input: I love Python
Output: Python love I

2. Method 1: Using split and reverse

sentence = input("Enter sentence: ")
words = sentence.split()

print(" ".join(words[::-1]))

This is the simplest and most Pythonic approach.

3. Method 2: Using Loop

sentence = input()
words = sentence.split()

reversed_words = []

for i in range(len(words)-1, -1, -1):
    reversed_words.append(words[i])

print(" ".join(reversed_words))

Manually builds reversed list.

4. Method 3: Using Stack

sentence = input()
stack = sentence.split()

result = []
while stack:
    result.append(stack.pop())

print(" ".join(result))

Uses LIFO principle of stack.

5. Method 4: Using Function

def reverse_words(s):
    return " ".join(s.split()[::-1])

print(reverse_words("Hello World Python"))

Encapsulates logic for reuse.

6. Method 5: Handling Edge Cases

sentence = input().strip()

if not sentence:
    print("Empty input")
else:
    print(" ".join(sentence.split()[::-1]))

Handles empty or whitespace-only input.

7. Algorithm

1. Split sentence into words.

2. Reverse word list.

3. Join words back into sentence.

4. Print result.

8. Common Mistakes

1. Reversing characters instead of words.

2. Not handling extra spaces.

3. Forgetting split/join usage.

4. Empty input not handled.

9. Applications

1. Text processing.

2. Chat applications.

3. NLP preprocessing.

4. Interview coding tests.

Conclusion

Reversing words in a sentence is a simple but powerful string manipulation problem.

Python makes it very easy using split and slicing techniques.