这段带有Python if语句和isinstance的代码可以调整以避免循环重复吗？

Question

我有一个脚本 - 一个生成器，它接受文件名或文件对象以及搜索词列表作为输入。生成器搜索文件的各行，并仅返回至少找到一个搜索词的那些行（整行）。

from io import TextIOBase
from typing import TextIO
import mimetypes


def find_lines(object_or_filename: TextIO | str, search_words: list) -> str:
    if isinstance(object_or_filename, str) and mimetypes.guess_type(object_or_filename)[0] == 'text/plain':
        with open(object_or_filename, 'r', encoding="utf-8") as file:
            for line in file:
                lower_line = line.lower()
                if any(word.lower() in lower_line.split() for word in search_words):
                    yield line.strip()
    elif isinstance(object_or_filename, TextIOBase):
        for line in object_or_filename:
            lower_line = line.lower()
            if any(word.lower() in lower_line.split() for word in search_words):
                yield line.strip()

有没有办法避免循环代码重复：

            for line in file:
                lower_line = line.lower()
                if any(word.lower() in lower_line.split() for word in search_words):
                    yield line.strip()

我希望这个循环只使用一次，但不知道如何实现。

Answer 1

感谢Barmar的评论我做了一个上下文管理器

with open(object_or_filename, 'r', encoding="utf-8") as file:

可选用

contextlib.nullcontext

。 已经解释了在这个问题中：

Python 3.7 及以上版本

Python 3.7 引入

contextlib.nullcontext

:

from contextlib import nullcontext

with get_stuff() if needs_with() else nullcontext() as gs:
    # do nearly the same large block of stuff,
    # involving gs or not, depending on needs_with()

注意

if needs_with() is False

，那么

gs

将是上下文块内的

None

。在这种情况下，如果您希望

gs

成为

something_else

，只需将

nullcontext()

替换为

nullcontext(something_else)

即可。

所以我的优化代码如下所示：

from io import TextIOBase
from typing import TextIO
import mimetypes
from contextlib import nullcontext

def find_lines(object_or_filename: TextIO | str, search_words: list) -> str:
    if isinstance(object_or_filename, str) and mimetypes.guess_type(object_or_filename)[0] == 'text/plain' or \
            isinstance(object_or_filename, TextIOBase):
        with open(object_or_filename, 'r', encoding="utf-8") if (isinstance(object_or_filename, str)) else \
                nullcontext(object_or_filename) as file:
            for line in file:
                lower_line = line.lower()
                if any(word.lower() in lower_line.split() for word in search_words):
                    yield line.strip()