Resolving JSONDecodeError When Reading JSON from a File in Python

Learn how to fix the common `JSONDecodeError` when reading from a file in Python with a step-by-step guide and improved code examples.
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Resolving JSONDecodeError When Reading JSON from a File in Python

When working with JSON data in Python, one common issue that developers encounter is the JSONDecodeError. This error typically arises when trying to parse JSON strings that are incorrectly formatted or improperly read from a file. In this article, we will explore a specific scenario that leads to this error and provide a clean solution to resolve it.

Understanding the Problem

Consider a situation where you are trying to read data from a file line by line, with each line containing valid JSON. For example, your JSON might look like this:

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

While attempting to read this data into a Python program, an error may occur, such as:

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

This error suggests that Python is not able to decode the JSON string properly. Let's see why this happens and how we can fix it.

The Cause of the Error

The issue stems from the misuse of the readline method in Python. In the original code provided, the line:

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

was mistakenly trying to read one byte from the file at a time, which is not how you want to read JSON data. This caused the JSON parser to fail because it was receiving an incomplete or malformed string.

The Solution

To solve this problem, you need to ensure that you read each line of the file correctly. Instead of using readline(i), you can simply iterate over the file object directly. Here's how to do it properly:

Step-by-Step Code Correction

Open the File: Use the open function to read the file containing the JSON data.

Iterate Through Each Line: Use a simple for-loop to go through each line in the file.

Here’s the corrected code:

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

Key Improvements

Using Context Manager: The with open(...) syntax ensures the file is properly closed after its suite finishes, which is a best practice.

Line Reading: Directly iterating over the file reads each line effectively without specifying a size, thus avoiding the JSON parsing issues encountered earlier.

Conclusion

By adhering to correct file reading practices when dealing with JSON data in Python, you can avoid the JSONDecodeError and ensure that your program runs smoothly. If you find yourself encountering this error, always check how you are reading your data and ensure that it is formatted correctly according to JSON standards.

Take these steps, implement the corrected code, and you will confidently parse JSON data from files in your Python projects without encountering decoding errors.