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libs/core/langchain_core/pydantic/__init__.py

@@ -0,0 +1,29 @@
+from importlib import metadata
+
+from .config import USE_PYDANTIC_V2
+
+## Create namespaces for pydantic v1 and v2.
+# This code must stay at the top of the file before other modules may
+# attempt to import pydantic since it adds pydantic_v1 and pydantic_v2 to sys.modules.
+#
+# This hack is done for the following reasons:
+# * Langchain will attempt to remain compatible with both pydantic v1 and v2 since
+#   both dependencies and dependents may be stuck on either version of v1 or v2.
+# * Creating namespaces for pydantic v1 and v2 should allow us to write code that
+#   unambiguously uses either v1 or v2 API.
+# * This change is easier to roll out and roll back.
+
+
+try:
+    if USE_PYDANTIC_V2:
+        from pydantic import *
+    else:
+        from pydantic.v1 import *  # noqa: F403 # type: ignore
+except ImportError:
+    from pydantic import *  # noqa: F403 # type: ignore
+
+
+try:
+    _PYDANTIC_MAJOR_VERSION: int = int(metadata.version("pydantic").split(".")[0])
+except metadata.PackageNotFoundError:
+    _PYDANTIC_MAJOR_VERSION = 0

libs/core/langchain_core/pydantic/config.py

@@ -0,0 +1,15 @@
+import os
+
+
+def _get_use_pydantic_v2() -> bool:
+    """Get the value of the LC_PYDANTIC_V2_UNSAFE environment variable."""
+    value = os.environ.get("LC_PYDANTIC_V2_UNSAFE", "false").lower()
+    if value == "true":
+        return True
+    elif value == "false":
+        return False
+    else:
+        raise ValueError(f"Invalid value for LANGCHAIN_PYDANTIC_V2_UNSAFE: {value}")
+
+
+USE_PYDANTIC_V2 = _get_use_pydantic_v2()

libs/core/langchain_core/pydantic/dataclasses.py

@@ -0,0 +1,9 @@
+from .config import USE_PYDANTIC_V2
+
+try:
+    if USE_PYDANTIC_V2:
+        from pydantic import *  # noqa: F403
+    else:
+        from pydantic.v1.dataclasses import *  # noqa: F403
+except ImportError:
+    from pydantic.dataclasses import *  # noqa: F403

libs/core/langchain_core/pydantic/main.py

@@ -0,0 +1,9 @@
+from .config import USE_PYDANTIC_V2
+
+try:
+    if USE_PYDANTIC_V2:
+        from pydantic.main import *
+    else:
+        from pydantic.v1.main import *  # noqa: F403
+except ImportError:
+    from pydantic.main import *  # noqa: F403