How to compare values in a list with a string?

Question

I want to create a script which should prevent equal sentences. Firstly, I thought that it was enough to just check if the previous and the current sentence are the same. But it turned out that no sentence should be duplicate. My first thought was to create a new list and save the created sentences in it. After that, the program should check if the new sentence is on the list. But it doesn’t work at all and I don’t know why. I hope you can help me.

*If you find any syntax mistakes it’s because I translated the script to English and did a mistake.

import random

sentence = ''
previous_sentence = ''
sentence_list = []

def create_sentence():
    names = ["x","y", "z"]
    descriptions = ["a","b", "Dc"]
    global sentence
    global previous_sentence
    global sentence_list



    while sentence == previous_sentence:
        sentence_list.append(sentence)
        name = random.choice(names)
        description = random.choice(descriptions)
        sentence = f'{name} is a {description}'
        if sentence == previous_sentence and sentence in sentence_list:
            name = random.choice(names)
            description = random.choice(descriptions)
            sentence = f'{name} is a {description}'
        else:
            previous_sentence = sentence
            return sentence
    else:
        prevoius_sentence = sentence
        return sentence       

for i in range(50):
    print(create_sentence())

Asked By: EnXan

||

Source

Answer 1

The script you’ve provided looks like it should prevent duplicate sentences from being generated, but there are a couple of issues with it that might be causing it not to work as intended.

First, in the while loop, you are adding the sentence to the sentence_list before checking if it’s a duplicate. So even if it’s a duplicate, it will still be added to the list, which means that the check for duplicates later on will not work correctly.

Next, inside the while loop, you have an if-else block where you are re-assigning the sentence variable with a new sentence if the current sentence is a duplicate. However, this block should be inside the while loop so that it’s executed every time a duplicate sentence is generated.

Additionally, you are using the same variable names for checking duplicate sentences and for the list of sentences, this can lead to confusion.

Here’s a revised version of your script that should work correctly:

import random

previous_sentence = ''
sentence_list = set()

def create_sentence():
    names = ["x","y", "z"]
    descriptions = ["a","b", "Dc"]
    global previous_sentence
    global sentence_list

    sentence = f'{random.choice(names)} is a {random.choice(descriptions)}'
    while sentence in sentence_list:
        sentence = f'{random.choice(names)} is a {random.choice(descriptions)}'
    sentence_list.add(sentence)
    previous_sentence = sentence
    return sentence

for i in range(50):
    print(create_sentence())

Answered By: long shen

Answer 2

I rewrite your code in a bit cleaner way without global variables and to make this code more reusable:

import random

def create_sentence(names, descriptions, sentence_list):
    name = random.choice(names)
    description = random.choice(descriptions)
    sentence = f'{name} is a {description}'
    while sentence in sentence_list:
        name = random.choice(names)
        description = random.choice(descriptions)
        sentence = f'{name} is a {description}'
    sentence_list.append(sentence)
    return sentence

def main():
    names = ["x","y", "z"]
    descriptions = ["a","b", "Dc"]
    sentence_list = []

    for i in range(50):
        print(create_sentence(names, descriptions, sentence_list))

if __name__ == '__main__':
    main()

The create_sentence() function uses a while loop that continues generating new sentences until a sentence is generated that is not already in the sentence_list. Once a unique sentence is generated, it is added to the sentence_list using the sentence_list.append(sentence) line.
The function also makes sure that a new sentence is created until it is different from the previous sentence, by checking if the sentence is already in the list before it appends it to the list. This ensures that the list will only contain unique sentences.
The function create_sentence() is separated from the main logic of the program, making it more reusable and easier to test.
The function takes in the names, descriptions, and sentence_list as arguments, making it more clear what data the function depends on.
The function uses a while loop instead of global variables to keep track of previous sentence.
The main function creates the variables and calls the create_sentence function in a for loop.
The main function is wrapped in a if name == 'main' block, it allows the code to be imported as a module without running the main function.
The variable and function names are in lower_case_with_underscores, making it more readable and consistent.
The code is more readable and easy to understand.
The if else block is removed as it’s not required.

Answered By: Patryk

How to compare values in a list with a string?

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