core: Add ruff rules PTH (pathlib) (#29338)

See https://docs.astral.sh/ruff/rules/#flake8-use-pathlib-pth

Co-authored-by: ccurme <chester.curme@gmail.com>

libs/core/langchain_core/callbacks/file.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from pathlib import Path
 from typing import TYPE_CHECKING, Any, Optional, TextIO, cast
 
 from langchain_core.callbacks import BaseCallbackHandler
@@ -30,7 +31,7 @@ class FileCallbackHandler(BaseCallbackHandler):
             mode: The mode to open the file in. Defaults to "a".
             color: The color to use for the text. Defaults to None.
         """
-        self.file = cast(TextIO, open(filename, mode, encoding="utf-8"))  # noqa: SIM115
+        self.file = cast(TextIO, Path(filename).open(mode, encoding="utf-8"))  # noqa: SIM115
         self.color = color
 
     def __del__(self) -> None:

libs/core/langchain_core/documents/base.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import contextlib
 import mimetypes
 from io import BufferedReader, BytesIO
-from pathlib import PurePath
+from pathlib import Path, PurePath
 from typing import TYPE_CHECKING, Any, Literal, Optional, Union, cast
 
 from pydantic import ConfigDict, Field, field_validator, model_validator
@@ -151,8 +151,7 @@ class Blob(BaseMedia):
     def as_string(self) -> str:
         """Read data as a string."""
         if self.data is None and self.path:
-            with open(str(self.path), encoding=self.encoding) as f:
-                return f.read()
+            return Path(self.path).read_text(encoding=self.encoding)
         elif isinstance(self.data, bytes):
             return self.data.decode(self.encoding)
         elif isinstance(self.data, str):
@@ -168,8 +167,7 @@ class Blob(BaseMedia):
         elif isinstance(self.data, str):
             return self.data.encode(self.encoding)
         elif self.data is None and self.path:
-            with open(str(self.path), "rb") as f:
-                return f.read()
+            return Path(self.path).read_bytes()
         else:
             msg = f"Unable to get bytes for blob {self}"
             raise ValueError(msg)
@@ -180,7 +178,7 @@ class Blob(BaseMedia):
         if isinstance(self.data, bytes):
             yield BytesIO(self.data)
         elif self.data is None and self.path:
-            with open(str(self.path), "rb") as f:
+            with Path(self.path).open("rb") as f:
                 yield f
         else:
             msg = f"Unable to convert blob {self}"

libs/core/langchain_core/language_models/llms.py

@@ -1402,7 +1402,7 @@ class BaseLLM(BaseLanguageModel[str], ABC):
             llm.save(file_path="path/llm.yaml")
         """
         # Convert file to Path object.
-        save_path = Path(file_path) if isinstance(file_path, str) else file_path
+        save_path = Path(file_path)
 
         directory_path = save_path.parent
         directory_path.mkdir(parents=True, exist_ok=True)
@@ -1411,10 +1411,10 @@ class BaseLLM(BaseLanguageModel[str], ABC):
         prompt_dict = self.dict()
 
         if save_path.suffix == ".json":
-            with open(file_path, "w") as f:
+            with save_path.open("w") as f:
                 json.dump(prompt_dict, f, indent=4)
         elif save_path.suffix.endswith((".yaml", ".yml")):
-            with open(file_path, "w") as f:
+            with save_path.open("w") as f:
                 yaml.dump(prompt_dict, f, default_flow_style=False)
         else:
             msg = f"{save_path} must be json or yaml"

libs/core/langchain_core/prompts/base.py

@@ -368,16 +368,16 @@ class BasePromptTemplate(
             raise NotImplementedError(msg)
 
         # Convert file to Path object.
-        save_path = Path(file_path) if isinstance(file_path, str) else file_path
+        save_path = Path(file_path)
 
         directory_path = save_path.parent
         directory_path.mkdir(parents=True, exist_ok=True)
 
         if save_path.suffix == ".json":
-            with open(file_path, "w") as f:
+            with save_path.open("w") as f:
                 json.dump(prompt_dict, f, indent=4)
         elif save_path.suffix.endswith((".yaml", ".yml")):
-            with open(file_path, "w") as f:
+            with save_path.open("w") as f:
                 yaml.dump(prompt_dict, f, default_flow_style=False)
         else:
             msg = f"{save_path} must be json or yaml"

libs/core/langchain_core/prompts/chat.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from pathlib import Path
 from typing import (
     TYPE_CHECKING,
     Annotated,
@@ -48,7 +49,6 @@ from langchain_core.utils.interactive_env import is_interactive_env
 
 if TYPE_CHECKING:
     from collections.abc import Sequence
-    from pathlib import Path
 
 
 class BaseMessagePromptTemplate(Serializable, ABC):
@@ -599,8 +599,7 @@ class _StringImageMessagePromptTemplate(BaseMessagePromptTemplate):
         Returns:
             A new instance of this class.
         """
-        with open(str(template_file)) as f:
-            template = f.read()
+        template = Path(template_file).read_text()
         return cls.from_template(template, input_variables=input_variables, **kwargs)
 
     def format_messages(self, **kwargs: Any) -> list[BaseMessage]:

libs/core/langchain_core/prompts/loading.py

@@ -53,8 +53,7 @@ def _load_template(var_name: str, config: dict) -> dict:
         template_path = Path(config.pop(f"{var_name}_path"))
         # Load the template.
         if template_path.suffix == ".txt":
-            with open(template_path) as f:
-                template = f.read()
+            template = template_path.read_text()
         else:
             raise ValueError
         # Set the template variable to the extracted variable.
@@ -67,10 +66,11 @@ def _load_examples(config: dict) -> dict:
     if isinstance(config["examples"], list):
         pass
     elif isinstance(config["examples"], str):
-        with open(config["examples"]) as f:
-            if config["examples"].endswith(".json"):
+        path = Path(config["examples"])
+        with path.open() as f:
+            if path.suffix == ".json":
                 examples = json.load(f)
-            elif config["examples"].endswith((".yaml", ".yml")):
+            elif path.suffix in {".yaml", ".yml"}:
                 examples = yaml.safe_load(f)
             else:
                 msg = "Invalid file format. Only json or yaml formats are supported."
@@ -168,13 +168,13 @@ def _load_prompt_from_file(
 ) -> BasePromptTemplate:
     """Load prompt from file."""
     # Convert file to a Path object.
-    file_path = Path(file) if isinstance(file, str) else file
+    file_path = Path(file)
     # Load from either json or yaml.
     if file_path.suffix == ".json":
-        with open(file_path, encoding=encoding) as f:
+        with file_path.open(encoding=encoding) as f:
             config = json.load(f)
     elif file_path.suffix.endswith((".yaml", ".yml")):
-        with open(file_path, encoding=encoding) as f:
+        with file_path.open(encoding=encoding) as f:
             config = yaml.safe_load(f)
     else:
         msg = f"Got unsupported file type {file_path.suffix}"

libs/core/langchain_core/prompts/prompt.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import warnings
+from pathlib import Path
 from typing import TYPE_CHECKING, Any, Optional, Union
 
 from pydantic import BaseModel, model_validator
@@ -17,8 +18,6 @@ from langchain_core.prompts.string import (
 )
 
 if TYPE_CHECKING:
-    from pathlib import Path
-
     from langchain_core.runnables.config import RunnableConfig
 
 
@@ -238,8 +237,7 @@ class PromptTemplate(StringPromptTemplate):
         Returns:
             The prompt loaded from the file.
         """
-        with open(str(template_file), encoding=encoding) as f:
-            template = f.read()
+        template = Path(template_file).read_text(encoding=encoding)
         if input_variables:
             warnings.warn(
                 "`input_variables' is deprecated and ignored.",

libs/core/langchain_core/runnables/graph_mermaid.py

@@ -2,6 +2,7 @@ import asyncio
 import base64
 import re
 from dataclasses import asdict
+from pathlib import Path
 from typing import Literal, Optional
 
 from langchain_core.runnables.graph import (
@@ -290,13 +291,9 @@ async def _render_mermaid_using_pyppeteer(
     img_bytes = await page.screenshot({"fullPage": False})
     await browser.close()
 
-    def write_to_file(path: str, bytes: bytes) -> None:
-        with open(path, "wb") as file:
-            file.write(bytes)
-
     if output_file_path is not None:
         await asyncio.get_event_loop().run_in_executor(
-            None, write_to_file, output_file_path, img_bytes
+            None, Path(output_file_path).write_bytes, img_bytes
         )
 
     return img_bytes
@@ -337,8 +334,7 @@ def _render_mermaid_using_api(
     if response.status_code == 200:
         img_bytes = response.content
         if output_file_path is not None:
-            with open(output_file_path, "wb") as file:
-                file.write(response.content)
+            Path(output_file_path).write_bytes(response.content)
 
         return img_bytes
     else:

libs/core/pyproject.toml

@@ -77,7 +77,7 @@ target-version = "py39"
 
 
 [tool.ruff.lint]
-select = [ "ANN", "ASYNC", "B", "C4", "COM", "DJ", "E", "EM", "EXE", "F", "FLY", "FURB", "I", "ICN", "INT", "LOG", "N", "NPY", "PD", "PIE", "Q", "RSE", "S", "SIM", "SLOT", "T10", "T201", "TC", "TID", "TRY", "UP", "W", "YTT",]
+select = [ "ANN", "ASYNC", "B", "C4", "COM", "DJ", "E", "EM", "EXE", "F", "FLY", "FURB", "I", "ICN", "INT", "LOG", "N", "NPY", "PD", "PIE", "PTH", "Q", "RSE", "S", "SIM", "SLOT", "T10", "T201", "TC", "TID", "TRY", "UP", "W", "YTT",]
 ignore = [ "ANN401", "COM812", "UP007", "S110", "S112", "TC001", "TC002", "TC003"]
 flake8-type-checking.runtime-evaluated-base-classes = ["pydantic.BaseModel","langchain_core.load.serializable.Serializable","langchain_core.runnables.base.RunnableSerializable"]
 flake8-annotations.allow-star-arg-any = true

libs/core/tests/unit_tests/prompts/test_prompt.py

@@ -354,7 +354,7 @@ def test_prompt_from_file_with_partial_variables() -> None:
     template = "This is a {foo} test {bar}."
     partial_variables = {"bar": "baz"}
     # when
-    with mock.patch("builtins.open", mock.mock_open(read_data=template)):
+    with mock.patch("pathlib.Path.open", mock.mock_open(read_data=template)):
         prompt = PromptTemplate.from_file(
             "mock_file_name", partial_variables=partial_variables
         )

libs/core/tests/unit_tests/test_imports.py

@@ -1,16 +1,13 @@
 import concurrent.futures
-import glob
 import importlib
 import subprocess
 from pathlib import Path
 
 
 def test_importable_all() -> None:
-    for path in glob.glob("../core/langchain_core/*"):
-        relative_path = Path(path).parts[-1]
-        if relative_path.endswith(".typed"):
-            continue
-        module_name = relative_path.split(".")[0]
+    for path in Path("../core/langchain_core/").glob("*"):
+        module_name = path.stem
+        if not module_name.startswith(".") and path.suffix != ".typed":
             module = importlib.import_module("langchain_core." + module_name)
             all_ = getattr(module, "__all__", [])
             for cls_ in all_:
@@ -37,11 +34,9 @@ def test_importable_all_via_subprocess() -> None:
           for one sequence of imports but not another.
     """
     module_names = []
-    for path in glob.glob("../core/langchain_core/*"):
-        relative_path = Path(path).parts[-1]
-        if relative_path.endswith(".typed"):
-            continue
-        module_name = relative_path.split(".")[0]
+    for path in Path("../core/langchain_core/").glob("*"):
+        module_name = path.stem
+        if not module_name.startswith(".") and path.suffix != ".typed":
             module_names.append(module_name)
 
     with concurrent.futures.ThreadPoolExecutor(max_workers=10) as executor: