Python解析含浮点值的JSON文件时遇TypeError问题求助

Hey there! Let's break down this error you're running into and fix it up.

What's Causing This Error? #

This error pops up when you try to use a string (like a JSON key) to index a list in Python. Lists only accept integer indices (0, 1, 2, etc.), so when you treat a list like it's a dictionary (which uses string keys), Python throws this TypeError.

Chances are, your JSON structure has a list where you expected a dictionary, or you're skipping a step where you need to index into a list first before accessing the key for your float value.

Example Scenario #

Let's use a common case that triggers this error:

Sample JSON Data

{
  "measurements": [
    {"temperature": 22.5},
    {"temperature": 23.1}
  ]
}

Broken Code (Causes the Error)

import json

with open('sensor_data.json', 'r') as f:
    parsed_data = json.load(f)

# ❌ Wrong: Trying to use 'temperature' (a string) to index the list parsed_data['measurements']
current_temp = parsed_data['measurements']['temperature']

When you run this, you'll get exactly the error you mentioned: TypeError: list indices must be integers, not str — because parsed_data['measurements'] is a list, not a dictionary.

How to Fix It #

You need to adjust your code to account for the list structure. Here are two common solutions:

1. Access a specific item in the list (use an integer index first):

   # ✅ Correct: First index into the list (e.g., 0 for the first item), then get the float value
   current_temp = parsed_data['measurements'][0]['temperature']
   print(current_temp)  # Output: 22.5
   

2. Loop through all items in the list (if you need every float value):

   # ✅ Correct: Iterate over the list to get each float value
   for measurement in parsed_data['measurements']:
       temp = measurement['temperature']
       print(f"Temperature reading: {temp}")
   

Troubleshooting Tips #

• Print your parsed data to inspect its structure. Use print(parsed_data) or pprint.pprint(parsed_data) (from the pprint module) to see clearly which parts are lists and which are dictionaries.
• Trace your access path: Double-check each step when accessing the float value. For example, if you have data['a']['b']['c'], confirm that data['a'] is a dict, data['a']['b'] is a list (if you're using an integer index next), etc.

内容的提问来源于stack exchange，提问作者user9300944