From 8e386613ace5b65af8ec655a8281ad2350c9139a Mon Sep 17 00:00:00 2001
From: engkheng <60956360+outday29@users.noreply.github.com>
Date: Wed, 19 Apr 2023 12:23:03 +0800
Subject: [PATCH] Import jinja2 only when used (#3123)

Addressing #3113
---
 langchain/prompts/base.py   | 2 +-
 langchain/prompts/prompt.py | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/langchain/prompts/base.py b/langchain/prompts/base.py
index 2038f301..c0c747ae 100644
--- a/langchain/prompts/base.py
+++ b/langchain/prompts/base.py
@@ -18,7 +18,7 @@ def jinja2_formatter(template: str, **kwargs: Any) -> str:
     try:
         from jinja2 import Template
     except ImportError:
-        raise ValueError(
+        raise ImportError(
             "jinja2 not installed, which is needed to use the jinja2_formatter. "
             "Please install it with `pip install jinja2`."
         )
diff --git a/langchain/prompts/prompt.py b/langchain/prompts/prompt.py
index 18a18514..af6ff29e 100644
--- a/langchain/prompts/prompt.py
+++ b/langchain/prompts/prompt.py
@@ -5,7 +5,6 @@ from pathlib import Path
 from string import Formatter
 from typing import Any, Dict, List, Set, Union
 
-from jinja2 import Environment, meta
 from pydantic import Extra, root_validator
 
 from langchain.prompts.base import (
@@ -16,6 +15,13 @@ from langchain.prompts.base import (
 
 
 def _get_jinja2_variables_from_template(template: str) -> Set[str]:
+    try:
+        from jinja2 import Environment, meta
+    except ImportError:
+        raise ImportError(
+            "jinja2 not installed, which is needed to use the jinja2_formatter. "
+            "Please install it with `pip install jinja2`."
+        )
     env = Environment()
     ast = env.parse(template)
     variables = meta.find_undeclared_variables(ast)