Editing Troubleshooting of Streamlit apps


== Troubleshooting of Streamlit Apps: LangChain RAG Integration Issues ==

I've built a Streamlit application that implements a RAG (Retrieval Augmented Generation) system using LangChain, Pinecone for vector storage, and LLMs (GPT/Claude). The app is experiencing a critical error when attempting to generate responses.

I've checked the logs from "Manage App" in Streamlit Cloud and found this error<ref>[https://discuss.streamlit.io/t/streamlit-logging-with-python-logger/51951 Streamlit Logging with Python Logger - Using Streamlit - Streamlit]</ref>:
<pre>
KeyError: "Input to ChatPromptTemplate is missing variables {'Source2', 'page', 'Source1'}.  Expected: ['Source1', 'Source2', 'chat''history', 'context', 'input', 'page'] Received: ['input', 'chat''history', 'context']"
</pre>
The error trace shows it's failing in <code>langchain_core/prompts/base.py</code> during the validation of input variables, suggesting a mismatch between what my chain provides and what the prompt template expects.

The issue appears to be in my document formatting pipeline. My current implementation:
* Retrieves documents from Pinecone
* Uses a <code>format_docs()</code> function that formats documents as strings
* Passes this to a LangChain prompt template from a Hub that expects additional variables

I've identified that my prompt template needs modification. Currently it contains:

'''Current Prompt (causing errors):'''
<pre>
Markdown format answer[1][2]
# Data Sources
1. {Source1}, p.{page}
2. {Source2}, p.{page}
</pre>

'''Proposed Modified Prompt:'''
<pre>
Markdown format answer[1][2]
# Data Sources ==
1. <Source1>, p.<page>
2. <Source2>, p.<page>

Replace <Source1>, <Source2>, etc., with the actual source names, and <page> with the relevant page numbers if available.
</pre>

To display curly braces as plain text in your prompt, use double curly braces {{kbd | key=<nowiki>{{</nowiki>}} and {{kbd | key=<nowiki>}}</nowiki>}} for escaping. Alternatively, you can replace them with {{kbd | key=<nowiki><</nowiki>}} and {{kbd | key=<nowiki>></nowiki>}} if that fits your use case.

Be cautious when using curly braces {{kbd | key=<nowiki>{xxx}</nowiki>}} in LangChain prompts - they're interpreted as variable placeholders. If you include them in your prompt, you must provide corresponding Python variables to pass these values. Be cautious when using curly braces {{kbd | key=<nowiki>{{xxx}}</nowiki>}} in LangChain prompts - they're interpreted as variable placeholders. If you include them in your prompt, you must provide corresponding Python variables to pass these values.<ref>[https://github.com/langchain-ai/langchain/issues/10639 When I use a prompt with "{", I get an error · Issue #10639 · langchain-ai/langchain]</ref>

== References ==
<references />

[[Category: Programming]]
[[Category: Python]]
[[Category: LangChain]]