Скачать или смотреть How to Output Multiple Identical Lines from a CSV File in Python

Discover how to retrieve and display multiple entries from a CSV file in Python using dictionaries and lists for an effective takeaway directory.
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How to Output Multiple Identical Lines from a CSV File in Python: A Step-by-Step Guide

If you're looking to create a takeaway directory that allows users to search by specific food types, ratings, or phone numbers, you may encounter a common problem. When attempting to retrieve multiple entries that match a search criterion from a CSV file, you might notice only one entry is displayed, even though you have several options available. This guide will guide you through the steps to efficiently print out multiple rows from a CSV file using Python.

Understanding the Problem

In the example scenario, the user is searching for "Pizza", and they only see one result instead of a comprehensive list of all pizza options available in the CSV file. The root of the issue lies in how the data is being stored after being read from the CSV file. Specifically, the code is using a dictionary to store the entries, which will only keep the last entry for each type of food because dictionary keys must be unique.

Desired Output

When a user searches for pizza, the expected output should be:

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

Solution Steps

To solve this problem effectively, we can leverage a Python module called collections which provides a flexible way to store multiple values for the same key. We will modify the existing code to use defaultdict instead of a regular dictionary.

Changes to the Code

Here's a step-by-step breakdown of how to implement the solution:

Import Required Libraries:
You'll need the csv library for reading CSV files and defaultdict from the collections module.

Initialize Data Structure:
Instead of using a regular dictionary, initialize a defaultdict(list). This will allow you to store a list of entries for each food type.

Read the CSV File:
As you read each row from the CSV, append the entry to the list corresponding to the food type.

Prompt for User Input:
Ask the user what type of food they are looking for.

Display Results:
Finally, print out all matching entries for the selected food type.

Revised Code

Below is the revised code incorporating the above steps:

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

Conclusion

By utilizing defaultdict to store lists of food entries, you can easily retrieve and print multiple matching lines from your CSV file. This approach not only resolves the initial issue but also enhances the functionality of your takeaway directory. Now, whether a user is seeking pizza, curry, or any other food type, they will see all available options – a win for user experience!

Be sure to implement this change in your code, and you'll effectively meet the needs of anyone searching for takeaway options in your directory. Happy coding!