字节JSON转换为字符串JSON后无法加载的问题求助

Hey there! Let's break down why your code is throwing that JSONDecodeError and how to fix it.

The Root Cause #

The byte data you're receiving has HTML entity-encoded quotes (") instead of standard JSON double quotes ("). When you decode the bytes to a string, you end up with something like this:

'{"_timestamp": 1636472787, "actual": 59.9, "target": 60.0}'

The json module can't recognize " as valid JSON syntax—it expects plain " characters, hence the "Expecting value" error at column 1.

The Solution #

You need to first convert those HTML entities back to regular characters before parsing the JSON. Python's built-in html module has a handy unescape() function for exactly this.

Here's your modified code:

import json
import html

def handle_msg(topic, message):
    # Decode bytes to string
    m = message.decode("utf-8")
    # Convert HTML entities to regular characters
    unescaped_m = html.unescape(m)
    # Now parse the valid JSON string
    print(json.loads(unescaped_m))

How It Works #

1. message.decode("utf-8") turns your byte data into a string (unchanged from your original code).
2. html.unescape(m) replaces all HTML entities (like ") with their corresponding characters (so " becomes "). The resulting string will be valid JSON:

   '{"_timestamp": 1636472787, "actual": 59.9, "target": 60.0}'
   

3. json.loads(unescaped_m) can now successfully parse the string into a Python dictionary.

Quick Test #

If you want to verify this works, you can run a small test snippet:

import json
import html

test_byte = b'{"_timestamp": 1636472787, "actual": 59.9, "target": 60.0}'
s = test_byte.decode("utf-8")
unescaped_s = html.unescape(s)
print(json.loads(unescaped_s))
# Output: {'_timestamp': 1636472787, 'actual': 59.9, 'target': 60.0}

内容的提问来源于stack exchange，提问作者Felix Dango