My Python Language Solution to Task 1 from The Weekly Challenge 299

1. Introduction

The Weekly Challenge, organized by Mohammad S. Anwar, is a friendly competition in which developers compete by solving a pair of tasks. It encourages participation from developers of all languages and levels through learning, sharing, and having fun.

Last week I competed in The Weekly Challenge 299 by solving Task 1: Replace Words. The task challenged developers to write a script that, when given an array and a sentence, replaced all words in the sentence that started with any of the words in the array.

In this post I present an overview of, and my solution to, Task 1: Replace Words from The Weekly Challenge 299 and finish with a brief conclusion.

2. Task 1: Replace Words

You are given an array of words and a sentence.

Write a script to replace all words in the given sentence that start with any of the words in the given array.

The Weekly Challenge 299, Task 1: Replace Words

Examples 1 - 3 illustrate the expected outputs from given inputs.

Example 1

Input: @words = ("cat", "bat", "rat")
       $sentence = "the cattle was rattle by the battery"
Output: "the cat was rat by the bat"

Output can be obtained by replacing any word in $sentence with $word from @words if it starts with $word, for example:

• The word cattle starts with the word cat, so replacing cattle with cat transforms the sentence into the cat was rattle by the battery.
• The word battery starts with the bat, so replacing battery with bat transforms the sentence into the cat was rattle by the bat.
• The word rattle starts with the word rat, so replacing rattle with rat, transforms the sentence into the cat was rattle by the bat.

Example 2

Input: @words = ("a", "b", "c")
       $sentence = "aab aac and cac bab"
Output: "a a a c b"

Example 3

Input: @words = ("man", "bike")
       $sentence = "the manager was hit by a biker"
Output: "the man was hit by a bike"

3. My solution

def replace_word(sentence, this_word):
    return ' '.join([this_word if word.startswith(this_word) else word for word in sentence.split(' ')])

def replace_words(words, sentence):
    for word in words:
        sentence = replace_word(sentence,
                                word)
    return sentence

My solution uses two functions: replace_word and replace_words.

The replace_word function replaces any word in the string sentence that starts with this_word with this_word using built-in string methods split, startswith, and join and a list comprehension.

• sentence.split(' ') splits sentence into a list of words using (' ') as a delimiter.
• The list comprehension [this_word if word.startswith(this_word) else word for word in...] builds another list of words from the split sentence list, replacing a word with this_word when it startswith the this_word.
• ' '.join(...) concatenates the second list into a string using (' ')
• return returns the string

The replace_words function successively applies replace_word to sentence for each word in the array words. It then returns the transformed sentence.

4. Conclusion

In this post I presented an overview of, and my solution to, Task 1: Replace Words from The Weekly Challenge 299.

Since I used built-in methods like split, join, and startswith in my solution, it is straightforward, verbose, and maybe easy to understand. Such an approach may be helpful to you if you are new to Python, new to programming, or unfamiliar with regular expressions.