Lesson 1
Manipulating Strings: Reversing Words in a Sentence
Introduction

Hello, and welcome! Are you ready to take your string manipulation skills in Python to the next level? Today, we'll explore a task that not only enhances your understanding of strings but also trains your ability to think creatively. The task at hand involves splitting a string into words, then reversing each word as if reflected in a mirror. Intrigued? Let's dive right in!

Task Statement and Description

Consider a string filled with words. Your task is to write a Python function that accepts such a string. It then takes each of those words, reverses their character order, and, finally, stitches them all together to form a new string with reversed words.

Here's what you need to keep in mind:

  • The input string will contain between 1 and 100 words.
  • Each word is a sequence of characters separated by white space.
  • A word is composed of characters ranging from a to z, A to Z, 0 to 9, or even an underscore _.
  • The given string will not start or end with a space - double spaces will not appear either.
  • After reversing the words, your program should return a single string with the words preserving their original order.

Example

Suppose that the input string is "Hello neat pythonistas_123".

The function will work on this in the following fashion:

  • 'Hello' becomes 'olleH'
  • 'neat' becomes 'taen'
  • 'pythonistas_123' becomes '321_satsinohtyp'

The function now combines the obtained strings into one string, resulting in "olleH taen 321_satsinohtyp".

Therefore, if solution("Hello neat pythonistas_123") is called, the returned value should be "olleH taen 321_satsinohtyp".

Let's start breaking this down!

Step-by-Step Solution Building: Step 1

Our very first step requires us to separate the words in the sentence. Python provides us with a built-in split() function, which breaks a given string at a specified separator and outputs a list of words. If no argument is provided to the split() function, it defaults to using space as the separator. Here is a sample code to illustrate this:

Python
1# an initial example string 2input_str = "Hello neat pythonistas_123" 3 4# split the string into words 5words = input_str.split() 6 7print(words)

You will see ['Hello', 'neat', 'pythonistas_123'] printed out.

Step-by-Step Solution Building: Step 2

We've successfully extracted the words from the sentence, but they're not reversed yet. Python's reversed() function comes to the rescue here. However, it returns something called an iterable and not a string directly. To convert this back to a string format, you can use the join() function. Let's add these lines to our existing code:

Python
1# an example string 2input_str = "Hello neat pythonistas_123" 3 4# split the string into words 5words = input_str.split() 6 7# reverse each word 8reversed_words = [''.join(reversed(word)) for word in words] 9 10print(reversed_words)

Aha! Now you can see the reversed words: ['olleH', 'taen', '321_satsinohtyp'].

Step-by-Step Solution Building: Step 3

Finally, we need to bring these reversed words back together again into a string format, using space as a separator. We get to use join() again for this. We call join() on the string ' ', which acts as a spacer between the words. Resultantly, our words are not squashed together when we form them into one string. Here's the code to complete our task:

Python
1def solution(input_str): 2 # split the string into words 3 words = input_str.split() 4 5 # reverse each word 6 reversed_words = [''.join(reversed(word)) for word in words] 7 8 # join the words back together with space as a separator 9 result = ' '.join(reversed_words) 10 11 return result 12 13# Now we call the function and print the returned result outside of the function 14print(solution("Hello neat pythonistas_123")) # this will print: 'olleH taen 321_satsinohtyp'
Lesson Summary

Well done! By completing this lesson, you've gained proficiency in manipulating strings in Python, especially when it comes to reversing the order of characters in a word. I hope you're feeling more confident and enthusiastic about your Python skills. Remember, the key to mastery is regular practice. Therefore, take a moment to explore related problems and practice what you’ve learned. It's all part of the joy of learning!

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