# langchain_classic > Python package 📖 [View in docs](https://reference.langchain.com/python/langchain-classic) ## Classes - [`BaseMemory`](https://reference.langchain.com/python/langchain-classic/base_memory/BaseMemory) - [`ModelLaboratory`](https://reference.langchain.com/python/langchain-classic/model_laboratory/ModelLaboratory) - [`BaseSingleActionAgent`](https://reference.langchain.com/python/langchain-classic/agents/agent/BaseSingleActionAgent) - [`BaseMultiActionAgent`](https://reference.langchain.com/python/langchain-classic/agents/agent/BaseMultiActionAgent) - [`AgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/agent/AgentOutputParser) - [`MultiActionAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/agent/MultiActionAgentOutputParser) - [`RunnableAgent`](https://reference.langchain.com/python/langchain-classic/agents/agent/RunnableAgent) - [`RunnableMultiActionAgent`](https://reference.langchain.com/python/langchain-classic/agents/agent/RunnableMultiActionAgent) - [`LLMSingleActionAgent`](https://reference.langchain.com/python/langchain-classic/agents/agent/LLMSingleActionAgent) - [`Agent`](https://reference.langchain.com/python/langchain-classic/agents/agent/Agent) - [`ExceptionTool`](https://reference.langchain.com/python/langchain-classic/agents/agent/ExceptionTool) - [`AgentExecutor`](https://reference.langchain.com/python/langchain-classic/agents/agent/AgentExecutor) - [`AgentType`](https://reference.langchain.com/python/langchain-classic/agents/agent_types/AgentType) - [`InvalidTool`](https://reference.langchain.com/python/langchain-classic/agents/tools/InvalidTool) - [`AgentScratchPadChatPromptTemplate`](https://reference.langchain.com/python/langchain-classic/agents/schema/AgentScratchPadChatPromptTemplate) - [`AgentExecutorIterator`](https://reference.langchain.com/python/langchain-classic/agents/agent_iterator/AgentExecutorIterator) - [`OpenAIToolsAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/openai_tools/OpenAIToolsAgentOutputParser) - [`SelfAskOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/self_ask/SelfAskOutputParser) - [`OpenAIFunctionsAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/openai_functions/OpenAIFunctionsAgentOutputParser) - [`ReActJsonSingleInputOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/react_json_single_input/ReActJsonSingleInputOutputParser) - [`XMLAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/xml/XMLAgentOutputParser) - [`ReActSingleInputOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/react_single_input/ReActSingleInputOutputParser) - [`ToolAgentAction`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/tools/ToolAgentAction) - [`ToolsAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/tools/ToolsAgentOutputParser) - [`JSONAgentOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/json/JSONAgentOutputParser) - [`StructuredChatAgent`](https://reference.langchain.com/python/langchain-classic/agents/structured_chat/base/StructuredChatAgent) - [`StructuredChatOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/structured_chat/output_parser/StructuredChatOutputParser) - [`StructuredChatOutputParserWithRetries`](https://reference.langchain.com/python/langchain-classic/agents/structured_chat/output_parser/StructuredChatOutputParserWithRetries) - [`OpenAIMultiFunctionsAgent`](https://reference.langchain.com/python/langchain-classic/agents/openai_functions_multi_agent/base/OpenAIMultiFunctionsAgent) - [`SelfAskWithSearchAgent`](https://reference.langchain.com/python/langchain-classic/agents/self_ask_with_search/base/SelfAskWithSearchAgent) - [`SelfAskWithSearchChain`](https://reference.langchain.com/python/langchain-classic/agents/self_ask_with_search/base/SelfAskWithSearchChain) - [`AgentTokenBufferMemory`](https://reference.langchain.com/python/langchain-classic/agents/openai_functions_agent/agent_token_buffer_memory/AgentTokenBufferMemory) - [`OpenAIFunctionsAgent`](https://reference.langchain.com/python/langchain-classic/agents/openai_functions_agent/base/OpenAIFunctionsAgent) - [`XMLAgent`](https://reference.langchain.com/python/langchain-classic/agents/xml/base/XMLAgent) - [`ConversationalChatAgent`](https://reference.langchain.com/python/langchain-classic/agents/conversational_chat/base/ConversationalChatAgent) - [`ConvoOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/conversational_chat/output_parser/ConvoOutputParser) - [`ChainConfig`](https://reference.langchain.com/python/langchain-classic/agents/mrkl/base/ChainConfig) - [`ZeroShotAgent`](https://reference.langchain.com/python/langchain-classic/agents/mrkl/base/ZeroShotAgent) - [`MRKLChain`](https://reference.langchain.com/python/langchain-classic/agents/mrkl/base/MRKLChain) - [`MRKLOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/mrkl/output_parser/MRKLOutputParser) - [`VectorStoreInfo`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/vectorstore/toolkit/VectorStoreInfo) - [`VectorStoreToolkit`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/vectorstore/toolkit/VectorStoreToolkit) - [`VectorStoreRouterToolkit`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/vectorstore/toolkit/VectorStoreRouterToolkit) - [`ReActDocstoreAgent`](https://reference.langchain.com/python/langchain-classic/agents/react/base/ReActDocstoreAgent) - [`DocstoreExplorer`](https://reference.langchain.com/python/langchain-classic/agents/react/base/DocstoreExplorer) - [`ReActTextWorldAgent`](https://reference.langchain.com/python/langchain-classic/agents/react/base/ReActTextWorldAgent) - [`ReActChain`](https://reference.langchain.com/python/langchain-classic/agents/react/base/ReActChain) - [`ReActOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/react/output_parser/ReActOutputParser) - [`OpenAIAssistantFinish`](https://reference.langchain.com/python/langchain-classic/agents/openai_assistant/base/OpenAIAssistantFinish) - [`OpenAIAssistantAction`](https://reference.langchain.com/python/langchain-classic/agents/openai_assistant/base/OpenAIAssistantAction) - [`OpenAIAssistantRunnable`](https://reference.langchain.com/python/langchain-classic/agents/openai_assistant/base/OpenAIAssistantRunnable) - [`ChatAgent`](https://reference.langchain.com/python/langchain-classic/agents/chat/base/ChatAgent) - [`ChatOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/chat/output_parser/ChatOutputParser) - [`ConversationalAgent`](https://reference.langchain.com/python/langchain-classic/agents/conversational/base/ConversationalAgent) - [`ConvoOutputParser`](https://reference.langchain.com/python/langchain-classic/agents/conversational/output_parser/ConvoOutputParser) - [`EncoderBackedStore`](https://reference.langchain.com/python/langchain-classic/storage/encoder_backed/EncoderBackedStore) - [`LocalFileStore`](https://reference.langchain.com/python/langchain-classic/storage/file_system/LocalFileStore) - [`DatetimeOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/datetime/DatetimeOutputParser) - [`BooleanOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/boolean/BooleanOutputParser) - [`EnumOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/enum/EnumOutputParser) - [`ResponseSchema`](https://reference.langchain.com/python/langchain-classic/output_parsers/structured/ResponseSchema) - [`StructuredOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/structured/StructuredOutputParser) - [`RegexParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/regex/RegexParser) - [`RegexDictParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/regex_dict/RegexDictParser) - [`RetryOutputParserRetryChainInput`](https://reference.langchain.com/python/langchain-classic/output_parsers/retry/RetryOutputParserRetryChainInput) - [`RetryWithErrorOutputParserRetryChainInput`](https://reference.langchain.com/python/langchain-classic/output_parsers/retry/RetryWithErrorOutputParserRetryChainInput) - [`RetryOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/retry/RetryOutputParser) - [`RetryWithErrorOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/retry/RetryWithErrorOutputParser) - [`PandasDataFrameOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/pandas_dataframe/PandasDataFrameOutputParser) - [`YamlOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/yaml/YamlOutputParser) - [`OutputFixingParserRetryChainInput`](https://reference.langchain.com/python/langchain-classic/output_parsers/fix/OutputFixingParserRetryChainInput) - [`OutputFixingParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/fix/OutputFixingParser) - [`CombiningOutputParser`](https://reference.langchain.com/python/langchain-classic/output_parsers/combining/CombiningOutputParser) - [`OpenAIFunction`](https://reference.langchain.com/python/langchain-classic/runnables/openai_functions/OpenAIFunction) - [`OpenAIFunctionsRouter`](https://reference.langchain.com/python/langchain-classic/runnables/openai_functions/OpenAIFunctionsRouter) - [`HubRunnable`](https://reference.langchain.com/python/langchain-classic/runnables/hub/HubRunnable) - [`AsyncFinalIteratorCallbackHandler`](https://reference.langchain.com/python/langchain-classic/callbacks/streaming_aiter_final_only/AsyncFinalIteratorCallbackHandler) - [`AsyncIteratorCallbackHandler`](https://reference.langchain.com/python/langchain-classic/callbacks/streaming_aiter/AsyncIteratorCallbackHandler) - [`FinalStreamingStdOutCallbackHandler`](https://reference.langchain.com/python/langchain-classic/callbacks/streaming_stdout_final_only/FinalStreamingStdOutCallbackHandler) - [`LoggingCallbackHandler`](https://reference.langchain.com/python/langchain-classic/callbacks/tracers/logging/LoggingCallbackHandler) - [`StringRunMapper`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/StringRunMapper) - [`LLMStringRunMapper`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/LLMStringRunMapper) - [`ChainStringRunMapper`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/ChainStringRunMapper) - [`ToolStringRunMapper`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/ToolStringRunMapper) - [`StringExampleMapper`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/StringExampleMapper) - [`StringRunEvaluatorChain`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/string_run_evaluator/StringRunEvaluatorChain) - [`EvalConfig`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/EvalConfig) - [`SingleKeyEvalConfig`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/SingleKeyEvalConfig) - [`RunEvalConfig`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig) - [`Criteria`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/Criteria) - [`LabeledCriteria`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/LabeledCriteria) - [`EmbeddingDistance`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/EmbeddingDistance) - [`StringDistance`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/StringDistance) - [`QA`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/QA) - [`ContextQA`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/ContextQA) - [`CoTQA`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/CoTQA) - [`JsonValidity`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/JsonValidity) - [`JsonEqualityEvaluator`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/JsonEqualityEvaluator) - [`ExactMatch`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/ExactMatch) - [`RegexMatch`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/RegexMatch) - [`ScoreString`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/ScoreString) - [`LabeledScoreString`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/RunEvalConfig/LabeledScoreString) - [`ProgressBarCallback`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/progress/ProgressBarCallback) - [`InputFormatError`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/InputFormatError) - [`TestResult`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/TestResult) - [`EvalError`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/EvalError) - [`ChatModelInput`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/ChatModelInput) - [`CacheBackedEmbeddings`](https://reference.langchain.com/python/langchain-classic/embeddings/cache/CacheBackedEmbeddings) - [`BaseChatMemory`](https://reference.langchain.com/python/langchain-classic/memory/chat_memory/BaseChatMemory) - [`SummarizerMixin`](https://reference.langchain.com/python/langchain-classic/memory/summary/SummarizerMixin) - [`ConversationSummaryMemory`](https://reference.langchain.com/python/langchain-classic/memory/summary/ConversationSummaryMemory) - [`SimpleMemory`](https://reference.langchain.com/python/langchain-classic/memory/simple/SimpleMemory) - [`BaseEntityStore`](https://reference.langchain.com/python/langchain-classic/memory/entity/BaseEntityStore) - [`InMemoryEntityStore`](https://reference.langchain.com/python/langchain-classic/memory/entity/InMemoryEntityStore) - [`UpstashRedisEntityStore`](https://reference.langchain.com/python/langchain-classic/memory/entity/UpstashRedisEntityStore) - [`RedisEntityStore`](https://reference.langchain.com/python/langchain-classic/memory/entity/RedisEntityStore) - [`SQLiteEntityStore`](https://reference.langchain.com/python/langchain-classic/memory/entity/SQLiteEntityStore) - [`ConversationEntityMemory`](https://reference.langchain.com/python/langchain-classic/memory/entity/ConversationEntityMemory) - [`CombinedMemory`](https://reference.langchain.com/python/langchain-classic/memory/combined/CombinedMemory) - [`ConversationTokenBufferMemory`](https://reference.langchain.com/python/langchain-classic/memory/token_buffer/ConversationTokenBufferMemory) - [`VectorStoreRetrieverMemory`](https://reference.langchain.com/python/langchain-classic/memory/vectorstore/VectorStoreRetrieverMemory) - [`ConversationBufferMemory`](https://reference.langchain.com/python/langchain-classic/memory/buffer/ConversationBufferMemory) - [`ConversationStringBufferMemory`](https://reference.langchain.com/python/langchain-classic/memory/buffer/ConversationStringBufferMemory) - [`ConversationBufferWindowMemory`](https://reference.langchain.com/python/langchain-classic/memory/buffer_window/ConversationBufferWindowMemory) - [`ReadOnlySharedMemory`](https://reference.langchain.com/python/langchain-classic/memory/readonly/ReadOnlySharedMemory) - [`ConversationSummaryBufferMemory`](https://reference.langchain.com/python/langchain-classic/memory/summary_buffer/ConversationSummaryBufferMemory) - [`ConversationVectorStoreTokenBufferMemory`](https://reference.langchain.com/python/langchain-classic/memory/vectorstore_token_buffer_memory/ConversationVectorStoreTokenBufferMemory) - [`LLMChain`](https://reference.langchain.com/python/langchain-classic/chains/llm/LLMChain) - [`Chain`](https://reference.langchain.com/python/langchain-classic/chains/base/Chain) - [`OpenAIModerationChain`](https://reference.langchain.com/python/langchain-classic/chains/moderation/OpenAIModerationChain) - [`TransformChain`](https://reference.langchain.com/python/langchain-classic/chains/transform/TransformChain) - [`SequentialChain`](https://reference.langchain.com/python/langchain-classic/chains/sequential/SequentialChain) - [`SimpleSequentialChain`](https://reference.langchain.com/python/langchain-classic/chains/sequential/SimpleSequentialChain) - [`MapReduceChain`](https://reference.langchain.com/python/langchain-classic/chains/mapreduce/MapReduceChain) - [`BasePromptSelector`](https://reference.langchain.com/python/langchain-classic/chains/prompt_selector/BasePromptSelector) - [`ConditionalPromptSelector`](https://reference.langchain.com/python/langchain-classic/chains/prompt_selector/ConditionalPromptSelector) - [`InputType`](https://reference.langchain.com/python/langchain-classic/chains/conversational_retrieval/base/InputType) - [`BaseConversationalRetrievalChain`](https://reference.langchain.com/python/langchain-classic/chains/conversational_retrieval/base/BaseConversationalRetrievalChain) - [`ConversationalRetrievalChain`](https://reference.langchain.com/python/langchain-classic/chains/conversational_retrieval/base/ConversationalRetrievalChain) - [`ChatVectorDBChain`](https://reference.langchain.com/python/langchain-classic/chains/conversational_retrieval/base/ChatVectorDBChain) - [`ElasticsearchDatabaseChain`](https://reference.langchain.com/python/langchain-classic/chains/elasticsearch_database/base/ElasticsearchDatabaseChain) - [`StructuredQueryOutputParser`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/StructuredQueryOutputParser) - [`ISO8601Date`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/parser/ISO8601Date) - [`ISO8601DateTime`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/parser/ISO8601DateTime) - [`QueryTransformer`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/parser/QueryTransformer) - [`AttributeInfo`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/schema/AttributeInfo) - [`LoadingCallable`](https://reference.langchain.com/python/langchain-classic/chains/question_answering/chain/LoadingCallable) - [`FactWithEvidence`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/citation_fuzzy_match/FactWithEvidence) - [`QuestionAnswer`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/citation_fuzzy_match/QuestionAnswer) - [`SimpleRequestChain`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/openapi/SimpleRequestChain) - [`AnswerWithSources`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/qa_with_structure/AnswerWithSources) - [`FinishedOutputParser`](https://reference.langchain.com/python/langchain-classic/chains/flare/prompts/FinishedOutputParser) - [`QuestionGeneratorChain`](https://reference.langchain.com/python/langchain-classic/chains/flare/base/QuestionGeneratorChain) - [`FlareChain`](https://reference.langchain.com/python/langchain-classic/chains/flare/base/FlareChain) - [`QAGenerationChain`](https://reference.langchain.com/python/langchain-classic/chains/qa_generation/base/QAGenerationChain) - [`LoadingCallable`](https://reference.langchain.com/python/langchain-classic/chains/summarize/chain/LoadingCallable) - [`LLMCheckerChain`](https://reference.langchain.com/python/langchain-classic/chains/llm_checker/base/LLMCheckerChain) - [`BaseQAWithSourcesChain`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/base/BaseQAWithSourcesChain) - [`QAWithSourcesChain`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/base/QAWithSourcesChain) - [`RetrievalQAWithSourcesChain`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/retrieval/RetrievalQAWithSourcesChain) - [`VectorDBQAWithSourcesChain`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/vector_db/VectorDBQAWithSourcesChain) - [`LoadingCallable`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/loading/LoadingCallable) - [`APIChain`](https://reference.langchain.com/python/langchain-classic/chains/api/base/APIChain) - [`ConversationChain`](https://reference.langchain.com/python/langchain-classic/chains/conversation/base/ConversationChain) - [`ElementInViewPort`](https://reference.langchain.com/python/langchain-classic/chains/natbot/crawler/ElementInViewPort) - [`Crawler`](https://reference.langchain.com/python/langchain-classic/chains/natbot/crawler/Crawler) - [`NatBotChain`](https://reference.langchain.com/python/langchain-classic/chains/natbot/base/NatBotChain) - [`SQLInput`](https://reference.langchain.com/python/langchain-classic/chains/sql_database/query/SQLInput) - [`SQLInputWithTables`](https://reference.langchain.com/python/langchain-classic/chains/sql_database/query/SQLInputWithTables) - [`LLMMathChain`](https://reference.langchain.com/python/langchain-classic/chains/llm_math/base/LLMMathChain) - [`Route`](https://reference.langchain.com/python/langchain-classic/chains/router/base/Route) - [`RouterChain`](https://reference.langchain.com/python/langchain-classic/chains/router/base/RouterChain) - [`MultiRouteChain`](https://reference.langchain.com/python/langchain-classic/chains/router/base/MultiRouteChain) - [`MultiRetrievalQAChain`](https://reference.langchain.com/python/langchain-classic/chains/router/multi_retrieval_qa/MultiRetrievalQAChain) - [`LLMRouterChain`](https://reference.langchain.com/python/langchain-classic/chains/router/llm_router/LLMRouterChain) - [`RouterOutputParser`](https://reference.langchain.com/python/langchain-classic/chains/router/llm_router/RouterOutputParser) - [`EmbeddingRouterChain`](https://reference.langchain.com/python/langchain-classic/chains/router/embedding_router/EmbeddingRouterChain) - [`MultiPromptChain`](https://reference.langchain.com/python/langchain-classic/chains/router/multi_prompt/MultiPromptChain) - [`HypotheticalDocumentEmbedder`](https://reference.langchain.com/python/langchain-classic/chains/hyde/base/HypotheticalDocumentEmbedder) - [`StuffDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/stuff/StuffDocumentsChain) - [`CombineDocsProtocol`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/CombineDocsProtocol) - [`AsyncCombineDocsProtocol`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/AsyncCombineDocsProtocol) - [`ReduceDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/ReduceDocumentsChain) - [`BaseCombineDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/base/BaseCombineDocumentsChain) - [`AnalyzeDocumentChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/base/AnalyzeDocumentChain) - [`MapReduceDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/map_reduce/MapReduceDocumentsChain) - [`MapRerankDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/map_rerank/MapRerankDocumentsChain) - [`RefineDocumentsChain`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/refine/RefineDocumentsChain) - [`BaseRetrievalQA`](https://reference.langchain.com/python/langchain-classic/chains/retrieval_qa/base/BaseRetrievalQA) - [`RetrievalQA`](https://reference.langchain.com/python/langchain-classic/chains/retrieval_qa/base/RetrievalQA) - [`VectorDBQA`](https://reference.langchain.com/python/langchain-classic/chains/retrieval_qa/base/VectorDBQA) - [`ConstitutionalChain`](https://reference.langchain.com/python/langchain-classic/chains/constitutional_ai/base/ConstitutionalChain) - [`ConstitutionalPrinciple`](https://reference.langchain.com/python/langchain-classic/chains/constitutional_ai/models/ConstitutionalPrinciple) - [`LLMSummarizationCheckerChain`](https://reference.langchain.com/python/langchain-classic/chains/llm_summarization_checker/base/LLMSummarizationCheckerChain) - [`EvaluatorType`](https://reference.langchain.com/python/langchain-classic/evaluation/schema/EvaluatorType) - [`LLMEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/schema/LLMEvalChain) - [`StringEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/schema/StringEvaluator) - [`PairwiseStringEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/schema/PairwiseStringEvaluator) - [`AgentTrajectoryEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/schema/AgentTrajectoryEvaluator) - [`TrajectoryEval`](https://reference.langchain.com/python/langchain-classic/evaluation/agents/trajectory_eval_chain/TrajectoryEval) - [`TrajectoryOutputParser`](https://reference.langchain.com/python/langchain-classic/evaluation/agents/trajectory_eval_chain/TrajectoryOutputParser) - [`TrajectoryEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/agents/trajectory_eval_chain/TrajectoryEvalChain) - [`QAEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/qa/eval_chain/QAEvalChain) - [`ContextQAEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/qa/eval_chain/ContextQAEvalChain) - [`CotQAEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/qa/eval_chain/CotQAEvalChain) - [`QAGenerateChain`](https://reference.langchain.com/python/langchain-classic/evaluation/qa/generate_chain/QAGenerateChain) - [`Criteria`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/Criteria) - [`CriteriaResultOutputParser`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/CriteriaResultOutputParser) - [`CriteriaEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/CriteriaEvalChain) - [`LabeledCriteriaEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/LabeledCriteriaEvalChain) - [`EmbeddingDistance`](https://reference.langchain.com/python/langchain-classic/evaluation/embedding_distance/base/EmbeddingDistance) - [`EmbeddingDistanceEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/embedding_distance/base/EmbeddingDistanceEvalChain) - [`PairwiseEmbeddingDistanceEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/embedding_distance/base/PairwiseEmbeddingDistanceEvalChain) - [`StringDistance`](https://reference.langchain.com/python/langchain-classic/evaluation/string_distance/base/StringDistance) - [`StringDistanceEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/string_distance/base/StringDistanceEvalChain) - [`PairwiseStringDistanceEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/string_distance/base/PairwiseStringDistanceEvalChain) - [`RegexMatchStringEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/regex_match/base/RegexMatchStringEvaluator) - [`JsonValidityEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/parsing/base/JsonValidityEvaluator) - [`JsonEqualityEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/parsing/base/JsonEqualityEvaluator) - [`JsonEditDistanceEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/parsing/json_distance/JsonEditDistanceEvaluator) - [`JsonSchemaEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/parsing/json_schema/JsonSchemaEvaluator) - [`ExactMatchStringEvaluator`](https://reference.langchain.com/python/langchain-classic/evaluation/exact_match/base/ExactMatchStringEvaluator) - [`PairwiseStringResultOutputParser`](https://reference.langchain.com/python/langchain-classic/evaluation/comparison/eval_chain/PairwiseStringResultOutputParser) - [`PairwiseStringEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/comparison/eval_chain/PairwiseStringEvalChain) - [`LabeledPairwiseStringEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/comparison/eval_chain/LabeledPairwiseStringEvalChain) - [`ScoreStringResultOutputParser`](https://reference.langchain.com/python/langchain-classic/evaluation/scoring/eval_chain/ScoreStringResultOutputParser) - [`ScoreStringEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/scoring/eval_chain/ScoreStringEvalChain) - [`LabeledScoreStringEvalChain`](https://reference.langchain.com/python/langchain-classic/evaluation/scoring/eval_chain/LabeledScoreStringEvalChain) - [`SearchType`](https://reference.langchain.com/python/langchain-classic/retrievers/multi_vector/SearchType) - [`MultiVectorRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/multi_vector/MultiVectorRetriever) - [`ParentDocumentRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/parent_document_retriever/ParentDocumentRetriever) - [`ContextualCompressionRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/contextual_compression/ContextualCompressionRetriever) - [`LineListOutputParser`](https://reference.langchain.com/python/langchain-classic/retrievers/multi_query/LineListOutputParser) - [`MultiQueryRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/multi_query/MultiQueryRetriever) - [`MergerRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/merger_retriever/MergerRetriever) - [`TimeWeightedVectorStoreRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/time_weighted_retriever/TimeWeightedVectorStoreRetriever) - [`EnsembleRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/ensemble/EnsembleRetriever) - [`RePhraseQueryRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/re_phraser/RePhraseQueryRetriever) - [`SelfQueryRetriever`](https://reference.langchain.com/python/langchain-classic/retrievers/self_query/base/SelfQueryRetriever) - [`LLMListwiseRerank`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/listwise_rerank/LLMListwiseRerank) - [`DocumentCompressorPipeline`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/base/DocumentCompressorPipeline) - [`CohereRerank`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/cohere_rerank/CohereRerank) - [`EmbeddingsFilter`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/embeddings_filter/EmbeddingsFilter) - [`CrossEncoderReranker`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/cross_encoder_rerank/CrossEncoderReranker) - [`NoOutputParser`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/chain_extract/NoOutputParser) - [`LLMChainExtractor`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/chain_extract/LLMChainExtractor) - [`LLMChainFilter`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/chain_filter/LLMChainFilter) - [`VectorStoreIndexWrapper`](https://reference.langchain.com/python/langchain-classic/indexes/vectorstore/VectorStoreIndexWrapper) - [`VectorstoreIndexCreator`](https://reference.langchain.com/python/langchain-classic/indexes/vectorstore/VectorstoreIndexCreator) - [`UpsertionRecord`](https://reference.langchain.com/python/langchain-classic/indexes/_sql_record_manager/UpsertionRecord) - [`SQLRecordManager`](https://reference.langchain.com/python/langchain-classic/indexes/_sql_record_manager/SQLRecordManager) ## Functions - [`push()`](https://reference.langchain.com/python/langchain-classic/hub/push) - [`pull()`](https://reference.langchain.com/python/langchain-classic/hub/pull) - [`get_runtime_environment()`](https://reference.langchain.com/python/langchain-classic/env/get_runtime_environment) - [`validate_tools_single_input()`](https://reference.langchain.com/python/langchain-classic/agents/utils/validate_tools_single_input) - [`initialize_agent()`](https://reference.langchain.com/python/langchain-classic/agents/initialize/initialize_agent) - [`load_agent_from_config()`](https://reference.langchain.com/python/langchain-classic/agents/loading/load_agent_from_config) - [`load_agent()`](https://reference.langchain.com/python/langchain-classic/agents/loading/load_agent) - [`create_json_chat_agent()`](https://reference.langchain.com/python/langchain-classic/agents/json_chat/base/create_json_chat_agent) - [`parse_ai_message_to_openai_tool_action()`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/openai_tools/parse_ai_message_to_openai_tool_action) - [`parse_ai_message_to_tool_action()`](https://reference.langchain.com/python/langchain-classic/agents/output_parsers/tools/parse_ai_message_to_tool_action) - [`create_structured_chat_agent()`](https://reference.langchain.com/python/langchain-classic/agents/structured_chat/base/create_structured_chat_agent) - [`format_log_to_messages()`](https://reference.langchain.com/python/langchain-classic/agents/format_scratchpad/log_to_messages/format_log_to_messages) - [`format_to_openai_function_messages()`](https://reference.langchain.com/python/langchain-classic/agents/format_scratchpad/openai_functions/format_to_openai_function_messages) - [`format_xml()`](https://reference.langchain.com/python/langchain-classic/agents/format_scratchpad/xml/format_xml) - [`format_log_to_str()`](https://reference.langchain.com/python/langchain-classic/agents/format_scratchpad/log/format_log_to_str) - [`format_to_tool_messages()`](https://reference.langchain.com/python/langchain-classic/agents/format_scratchpad/tools/format_to_tool_messages) - [`create_tool_calling_agent()`](https://reference.langchain.com/python/langchain-classic/agents/tool_calling_agent/base/create_tool_calling_agent) - [`create_self_ask_with_search_agent()`](https://reference.langchain.com/python/langchain-classic/agents/self_ask_with_search/base/create_self_ask_with_search_agent) - [`create_openai_functions_agent()`](https://reference.langchain.com/python/langchain-classic/agents/openai_functions_agent/base/create_openai_functions_agent) - [`create_xml_agent()`](https://reference.langchain.com/python/langchain-classic/agents/xml/base/create_xml_agent) - [`create_conversational_retrieval_agent()`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/conversational_retrieval/openai_functions/create_conversational_retrieval_agent) - [`create_vectorstore_agent()`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/vectorstore/base/create_vectorstore_agent) - [`create_vectorstore_router_agent()`](https://reference.langchain.com/python/langchain-classic/agents/agent_toolkits/vectorstore/base/create_vectorstore_router_agent) - [`create_openai_tools_agent()`](https://reference.langchain.com/python/langchain-classic/agents/openai_tools/base/create_openai_tools_agent) - [`create_react_agent()`](https://reference.langchain.com/python/langchain-classic/agents/react/agent/create_react_agent) - [`create_lc_store()`](https://reference.langchain.com/python/langchain-classic/storage/_lc_store/create_lc_store) - [`create_kv_docstore()`](https://reference.langchain.com/python/langchain-classic/storage/_lc_store/create_kv_docstore) - [`load_output_parser()`](https://reference.langchain.com/python/langchain-classic/output_parsers/loading/load_output_parser) - [`get_pydantic_major_version()`](https://reference.langchain.com/python/langchain-classic/utils/pydantic/get_pydantic_major_version) - [`StreamlitCallbackHandler()`](https://reference.langchain.com/python/langchain-classic/callbacks/streamlit/StreamlitCallbackHandler) - [`callback()`](https://reference.langchain.com/python/langchain-classic/callbacks/tracers/logging/LoggingCallbackHandler/__init__/callback) - [`random_name()`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/name_generation/random_name) - [`arun_on_dataset()`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/arun_on_dataset) - [`run_on_dataset()`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/run_on_dataset) - [`init_embeddings()`](https://reference.langchain.com/python/langchain-classic/embeddings/base/init_embeddings) - [`get_prompt_input_key()`](https://reference.langchain.com/python/langchain-classic/memory/utils/get_prompt_input_key) - [`init_chat_model()`](https://reference.langchain.com/python/langchain-classic/chat_models/base/init_chat_model) - [`create_retrieval_chain()`](https://reference.langchain.com/python/langchain-classic/chains/retrieval/create_retrieval_chain) - [`create_history_aware_retriever()`](https://reference.langchain.com/python/langchain-classic/chains/history_aware_retriever/create_history_aware_retriever) - [`generate_example()`](https://reference.langchain.com/python/langchain-classic/chains/example_generator/generate_example) - [`load_llm()`](https://reference.langchain.com/python/langchain-classic/chains/loading/load_llm) - [`load_llm_from_config()`](https://reference.langchain.com/python/langchain-classic/chains/loading/load_llm_from_config) - [`load_chain_from_config()`](https://reference.langchain.com/python/langchain-classic/chains/loading/load_chain_from_config) - [`load_chain()`](https://reference.langchain.com/python/langchain-classic/chains/loading/load_chain) - [`is_llm()`](https://reference.langchain.com/python/langchain-classic/chains/prompt_selector/is_llm) - [`is_chat_model()`](https://reference.langchain.com/python/langchain-classic/chains/prompt_selector/is_chat_model) - [`fix_filter_directive()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/fix_filter_directive) - [`construct_examples()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/construct_examples) - [`get_query_constructor_prompt()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/get_query_constructor_prompt) - [`load_query_constructor_chain()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/load_query_constructor_chain) - [`load_query_constructor_runnable()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/base/load_query_constructor_runnable) - [`v_args()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/parser/v_args) - [`get_parser()`](https://reference.langchain.com/python/langchain-classic/chains/query_constructor/parser/get_parser) - [`load_qa_chain()`](https://reference.langchain.com/python/langchain-classic/chains/question_answering/chain/load_qa_chain) - [`create_openai_fn_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/base/create_openai_fn_chain) - [`create_structured_output_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/base/create_structured_output_chain) - [`get_llm_kwargs()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/utils/get_llm_kwargs) - [`create_tagging_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/tagging/create_tagging_chain) - [`create_tagging_chain_pydantic()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/tagging/create_tagging_chain_pydantic) - [`create_extraction_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/extraction/create_extraction_chain) - [`create_extraction_chain_pydantic()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/extraction/create_extraction_chain_pydantic) - [`create_citation_fuzzy_match_runnable()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/citation_fuzzy_match/create_citation_fuzzy_match_runnable) - [`create_citation_fuzzy_match_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/citation_fuzzy_match/create_citation_fuzzy_match_chain) - [`openapi_spec_to_openai_fn()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/openapi/openapi_spec_to_openai_fn) - [`get_openapi_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/openapi/get_openapi_chain) - [`create_qa_with_structure_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/qa_with_structure/create_qa_with_structure_chain) - [`create_qa_with_sources_chain()`](https://reference.langchain.com/python/langchain-classic/chains/openai_functions/qa_with_structure/create_qa_with_sources_chain) - [`create_openai_fn_runnable()`](https://reference.langchain.com/python/langchain-classic/chains/structured_output/base/create_openai_fn_runnable) - [`create_structured_output_runnable()`](https://reference.langchain.com/python/langchain-classic/chains/structured_output/base/create_structured_output_runnable) - [`get_openai_output_parser()`](https://reference.langchain.com/python/langchain-classic/chains/structured_output/base/get_openai_output_parser) - [`load_summarize_chain()`](https://reference.langchain.com/python/langchain-classic/chains/summarize/chain/load_summarize_chain) - [`load_qa_with_sources_chain()`](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/loading/load_qa_with_sources_chain) - [`create_sql_query_chain()`](https://reference.langchain.com/python/langchain-classic/chains/sql_database/query/create_sql_query_chain) - [`create_extraction_chain_pydantic()`](https://reference.langchain.com/python/langchain-classic/chains/openai_tools/extraction/create_extraction_chain_pydantic) - [`create_stuff_documents_chain()`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/stuff/create_stuff_documents_chain) - [`split_list_of_docs()`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/split_list_of_docs) - [`collapse_docs()`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/collapse_docs) - [`acollapse_docs()`](https://reference.langchain.com/python/langchain-classic/chains/combine_documents/reduce/acollapse_docs) - [`get_type_to_cls_dict()`](https://reference.langchain.com/python/langchain-classic/llms/get_type_to_cls_dict) - [`load_dataset()`](https://reference.langchain.com/python/langchain-classic/evaluation/loading/load_dataset) - [`load_evaluator()`](https://reference.langchain.com/python/langchain-classic/evaluation/loading/load_evaluator) - [`load_evaluators()`](https://reference.langchain.com/python/langchain-classic/evaluation/loading/load_evaluators) - [`resolve_criteria()`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/resolve_criteria) - [`resolve_pairwise_criteria()`](https://reference.langchain.com/python/langchain-classic/evaluation/comparison/eval_chain/resolve_pairwise_criteria) - [`resolve_criteria()`](https://reference.langchain.com/python/langchain-classic/evaluation/scoring/eval_chain/resolve_criteria) - [`unique_by_key()`](https://reference.langchain.com/python/langchain-classic/retrievers/ensemble/unique_by_key) - [`default_get_input()`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/chain_extract/default_get_input) - [`default_get_input()`](https://reference.langchain.com/python/langchain-classic/retrievers/document_compressors/chain_filter/default_get_input) - [`create_importer()`](https://reference.langchain.com/python/langchain-classic/_api/module_import/create_importer) - [`is_interactive_env()`](https://reference.langchain.com/python/langchain-classic/_api/interactive_env/is_interactive_env) ## Types - [`RunnableAgentType`](https://reference.langchain.com/python/langchain-classic/agents/agent/RunnableAgentType) - [`AGENT_TYPE`](https://reference.langchain.com/python/langchain-classic/agents/types/AGENT_TYPE) - [`OutputType`](https://reference.langchain.com/python/langchain-classic/agents/openai_assistant/base/OutputType) - [`CUSTOM_EVALUATOR_TYPE`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/CUSTOM_EVALUATOR_TYPE) - [`SINGLE_EVAL_CONFIG_TYPE`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/config/SINGLE_EVAL_CONFIG_TYPE) - [`MODEL_OR_CHAIN_FACTORY`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/MODEL_OR_CHAIN_FACTORY) - [`MCF`](https://reference.langchain.com/python/langchain-classic/smith/evaluation/runner_utils/MCF) - [`CHAT_TURN_TYPE`](https://reference.langchain.com/python/langchain-classic/chains/conversational_retrieval/base/CHAT_TURN_TYPE) - [`CRITERIA_TYPE`](https://reference.langchain.com/python/langchain-classic/evaluation/criteria/eval_chain/CRITERIA_TYPE)