模块、包、异常和文件操作：把单个脚本拆成可维护程序

模块：拆分单个 Python 文件
包：组织一组相关模块
文件操作：让程序读取和保存外部数据
异常：让预期中的失败有明确出口

def load_text(path: str) -> str:
    ...

from text_loader import load_text

if __name__ == "__main__":
    main()

prompt_app/
├── app.py
├── data/
│   └── python.txt
└── knowledge/
    ├── __init__.py
    └── text_loader.py

from knowledge.text_loader import load_text

from pathlib import Path

data_path = Path("data") / "python.txt"

project_dir = Path(__file__).resolve().parent
data_path = project_dir / "data" / "python.txt"

with path.open("r", encoding="utf-8") as file:
    content = file.read()

from pathlib import Path

path = Path("note.txt")
content = path.read_text(encoding="utf-8")
print(content)

from pathlib import Path

path = Path("note.txt")

with path.open("r", encoding="utf-8") as file:
    for line_number, line in enumerate(file, start=1):
        print(line_number, line.rstrip("\n"))

from pathlib import Path

result_path = Path("result.txt")
result_path.write_text("第一次结果\n", encoding="utf-8")

with result_path.open("a", encoding="utf-8") as file:
    file.write("追加结果\n")
    file.writelines(["第三行\n", "第四行\n"])

from pathlib import Path

path = Path("data.bin")
path.write_bytes(b"abcdef")

with path.open("rb") as file:
    print(file.read(2))  # b'ab'
    print(file.tell())   # 2

    file.seek(0)
    print(file.read(3))  # b'abc'

from pathlib import Path

source = Path("source.bin")
target = Path("copy.bin")

with source.open("rb") as input_file, target.open("wb") as output_file:
    while chunk := input_file.read(8192):
        output_file.write(chunk)

from pathlib import Path

data_dir = Path("data")
data_dir.mkdir(parents=True, exist_ok=True)

for path in data_dir.glob("*.md"):
    print(path.name, path.suffix, path.stat().st_size)

try:
    result = risky_operation()
except SomeError as error:
    handle(error)
else:
    use(result)
finally:
    cleanup()

from pathlib import Path

try:
    content = Path("note.txt").read_text(encoding="utf-8")
except FileNotFoundError:
    print("文件不存在")
except UnicodeDecodeError:
    print("文件不是有效的 UTF-8 文本")
else:
    print(f"读取成功，共 {len(content)} 个字符")
finally:
    print("读取流程结束")

def validate_chunk_size(chunk_size: int) -> None:
    if chunk_size <= 0:
        raise ValueError("chunk_size 必须大于 0")

class DocumentLoadError(Exception):
    """文档无法进入后续处理流程。"""


def require_content(content: str) -> str:
    if not content.strip():
        raise DocumentLoadError("文档内容为空")
    return content.strip()

from pathlib import Path


def read_document(path: Path) -> str:
    return path.read_text(encoding="utf-8")


def build_context(path: Path) -> str:
    content = read_document(path)
    return content.strip()


try:
    context = build_context(Path("missing.txt"))
except FileNotFoundError as error:
    print(f"入口统一处理：{error}")

import json

data = json.loads('{"name": "Python"}')

from pathlib import Path

path = Path("note.txt")

import datetime as dt

today = dt.date.today()

import sys

for path in sys.path:
    print(path)

import json

print("loads" in dir(json))

prompt_app/
├── app.py
├── data/
│   └── python.txt
└── knowledge/
    ├── __init__.py
    └── text_loader.py

Python 的虚拟环境可以隔离不同项目的依赖。

from pathlib import Path


def load_text(path: Path) -> str:
    if not path.is_file():
        raise FileNotFoundError(f"文档不存在：{path}")

    content = path.read_text(encoding="utf-8").strip()
    if not content:
        raise ValueError(f"文档内容为空：{path}")

    return content

from pathlib import Path

from knowledge.text_loader import load_text


def main() -> None:
    project_dir = Path(__file__).resolve().parent
    document_path = project_dir / "data" / "python.txt"

    try:
        context = load_text(document_path)
    except FileNotFoundError as error:
        print(f"加载失败：{error}")
        return
    except UnicodeDecodeError:
        print("加载失败：文档不是有效的 UTF-8 文本")
        return
    except ValueError as error:
        print(f"加载失败：{error}")
        return

    question = "虚拟环境有什么作用？"
    prompt = f"请根据资料回答。\n\n资料：{context}\n\n问题：{question}"
    print(prompt)


if __name__ == "__main__":
    main()

python app.py

from pathlib import Path


def load_text(path: Path) -> str:
    content = path.read_text(encoding="utf-8").strip()
    if not content:
        raise ValueError("内容为空")
    return content


def load_directory(directory: Path) -> tuple[list[dict[str, str]], list[str]]:
    if not directory.is_dir():
        raise NotADirectoryError(f"目录不存在：{directory}")

    documents = []
    errors = []

    for path in sorted(directory.glob("*.txt")):
        try:
            content = load_text(path)
        except (OSError, UnicodeDecodeError, ValueError) as error:
            errors.append(f"{path.name}: {error}")
            continue

        documents.append({"title": path.stem, "content": content})

    return documents, errors

try:
    content = load_text(path)
except Exception:
    pass