Скачать или смотреть Creating Dictionaries from Lists with Multiple Values in Python

Learn how to effectively create dictionaries in Python that map product names to their corresponding prices and quantities, using data extracted from a file.
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Creating Dictionaries from Lists with Multiple Values in Python

When working with data in Python, especially when it comes from a file, you might encounter scenarios where you need to construct dictionaries that map keys (like product names) to multiple values (like prices and quantities). This guide will guide you through a common problem encountered when attempting to create such dictionaries using data from a text file. We will also explore the solution that can rectify the issues that arise during this process.

The Problem

Imagine you have a text file named Initial_inventory-1.txt that contains product information. Each line contains a product name, price, and quantity, separated by semicolons. You want to create two dictionaries: one for prices and another for quantities. The challenge, however, arises when your output includes unexpected values—specifically an incorrect mapping of the characters of the product name instead of just the name itself, alongside their prices and quantities.

Here’s an example of the incorrect implementation you might encounter:

[[See Video to Reveal this Text or Code Snippet]]

The key issue is that the loops are iterating over the characters of the product name instead of handling the data correctly.

The Solution

To solve this problem, we need to correctly extract the product name, price, and quantity from each line of the file and appropriately populate our dictionaries. Here’s a step-by-step guide to achieve it:

Step 1: Define the Function

We start by defining a function that opens the text file and reads its contents line by line.

Step 2: Split the Data Correctly

Utilize the split() method to separate the product name, price, and quantity right at the beginning of the loop. This will help in avoiding errors later on.

Step 3: Use setdefault() for Lists

Instead of using the product name directly as a key and replacing values in the dictionary, the setdefault() method will help maintain a list of values corresponding to each key.

Final Code Implementation

Here’s the updated version of the read_file function:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Main Function

Make sure you have a main function that initializes your dictionaries and calls the read_file function:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps and using the corrected code above, you can successfully map product names to their respective prices and quantities without confusion. This approach ensures clarity in your dictionary structure and avoids the issues of character iteration that can lead to erroneous outputs.

Now you're equipped to handle such data extraction tasks confidently. Happy coding!