Why Does `json.loads()` Throw a 'JSONDecodeError: Expecting Value' and How Can I Fix It?

JSONDecodeError: Expecting Value in Python

When attempting to parse JSON using the json.loads() function, an error message like "Expecting value: line 1 column 1 (char 0)" can arise. This error indicates that the input string provided does not conform to the expected JSON format.

Resolving the Issue

The most common cause of this error is an empty or incomplete response body. To resolve it, ensure that the following steps are followed:

1. Verify that the API call results in a non-empty response. An HTTP response status code in the 200 range should be returned.
2. Decode the response body using the UTF-8 encoding instead of Unicode. The json.loads() function can handle UTF-8-encoded data directly.
3. Consider using alternative libraries such as requests or httpx, which provide more user-friendly APIs and built-in JSON support.

Here is an example using the Requests package:

import requests

response = requests.get(url)
if response.status_code != 204:
    return response.json()

To safeguard against violations of HTTP standards, check the Content-Type header to verify that the server intended to deliver JSON. If a ValueError occurs while parsing the JSON, appropriate error handling can be implemented:

if (
    response.status_code != 204 and
    response.headers["content-type"].strip().startswith("application/json")
):
    try:
        return response.json()
    except ValueError:
        # Handle server misbehavior

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