Скачать или смотреть Solving Python Scrapy Issues: How to Properly Yield Data to a .json File

Discover effective solutions to troubleshoot your `Python Scrapy` code when yielding data to a JSON file. Learn simple fixes for common problems.
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This video is based on the question https://stackoverflow.com/q/73908758/ asked by the user 'Alexandre Nakicen' ( https://stackoverflow.com/u/17319060/ ) and on the answer https://stackoverflow.com/a/73908963/ provided by the user 'Md. Fazlul Hoque' ( https://stackoverflow.com/u/12848411/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Your Python Scrapy Yield to a JSON File

If you've ever tried to extract data using Python's Scrapy framework and found that your output JSON file is empty, you're not alone. This common issue can be frustrating for developers as they work to scrape websites for valuable data. In this guide, we'll uncover the reasons behind this problem and guide you through a well-structured solution to ensure your titles are successfully stored in a JSON file.

Understanding the Problem

You want to scrape book titles from a website using Scrapy and save them into a JSON file. While your code appears to be correct, the resulting JSON file is mysteriously empty. Therefore, let’s dig into the core of your scraping code and identify what went wrong.

Initial Attempts at Scraping

Your initial spider code looked like this:

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

In the terminal, you ran:

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

What happened? While the command successfully generated the books.json file, it was empty. However, when you attempted to write the entire response body to an HTML file, it worked flawlessly.

The Solution

There are crucial adjustments needed in your spider's parse method to properly yield data for the JSON output. Here’s a revised version of the spider that will correctly extract and format the titles:

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

Key Changes Explained

CSS Selector Adjustment:

Instead of directly fetching the titles using one CSS selector on the response, we first select the container of each book using:

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

This change ensures that we're iterating over each book individually.

Yielding Titles:

We yield the title for each book using:

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

This method allows Scrapy to collect each title in the appropriate dictionary format for JSON output.

Validating Results

Run the spider after making these changes:

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

Now, when you check books.json, you should see entries similar to the following:

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

Conclusion

By restructuring your Scrapy spider's parse method to accurately collect and yield book titles, you can ensure that your data is properly saved into a JSON file. This will significantly enhance your web scraping efforts and lead to successful data extraction. Remember, careful attention to your selection tactics and yielding methods can solve many common problems in Scrapy.

Happy Scraping!