TypeError
builtins.TypeError
Stack trace
Traceback (most recent call last):
File "app.py", line 42, in <module>
print(chunk['choices'][0]['delta']['content'])
TypeError: 'NoneType' object is not subscriptable Why it happens
OpenAI streaming responses send incremental 'delta' objects that may sometimes have 'content' set to None, especially for initial or empty messages. Code that assumes 'content' is always a string and tries to subscript or process it without checking for None will raise this error.
Detection
Check if the 'content' field in each streaming delta is None before processing or subscripting it, and log or handle such cases gracefully to avoid crashes.
Causes & fixes
The streaming delta message has 'content' set to None for initial or empty tokens.
Add a conditional check to verify 'content' is not None before accessing or processing it.
Code assumes every delta chunk contains a 'content' string without validation.
Use safe access patterns like 'if chunk['choices'][0]['delta'].get('content') is not None' before usage.
Using older or incorrect example code that does not handle None content in streaming responses.
Update code to follow the latest OpenAI SDK streaming examples that handle None content properly.
Code: broken vs fixed
from openai import OpenAI
import os
client = OpenAI(api_key=os.environ['OPENAI_API_KEY'])
response = client.chat.completions.create(
model="gpt-4o-mini",
messages=[{"role": "user", "content": "Say hi"}],
stream=True
)
for chunk in response:
# This line causes TypeError if content is None
print(chunk['choices'][0]['delta']['content']) # broken linefrom openai import OpenAI
import os
client = OpenAI(api_key=os.environ['OPENAI_API_KEY'])
response = client.chat.completions.create(
model="gpt-4o-mini",
messages=[{"role": "user", "content": "Say hi"}],
stream=True
)
for chunk in response:
content = chunk['choices'][0]['delta'].get('content')
if content is not None:
print(content) # fixed: check for None before printingWorkaround
Wrap the streaming loop in try/except TypeError and skip or log chunks where 'content' is None to continue processing without crashing.
Prevention
Always validate streaming delta content fields for None before processing, and use official SDK streaming examples that handle partial or empty deltas correctly.