llm_chain_fallbacks.py

from langchain import PromptTemplate, OpenAI, LLMChain

prompt_template = "What is a good name for a company that makes {product}?"

llm1 = OpenAI(model="foo", temperature=0)
llm_chain1 = LLMChain(
    llm=llm1,
    prompt=PromptTemplate.from_template(prompt_template)
)

llm2 = OpenAI(temperature=0)
llm_chain2 = LLMChain(
    llm=llm2,
    prompt=PromptTemplate.from_template(prompt_template)
)

llm_chain = llm_chain1.with_fallbacks([llm_chain2])

llm_chain.invoke({"product": "hi"})