How/where 要使用 os.path.sep？

Question

os.path.sep是操作系统用来分隔路径名组成部分的字符。

但是在os.path.join()中使用os.path.sep时，为什么会截断路径？

示例：

而不是'home/python'，os.path.join returns '/python'：

>>> import os
>>> os.path.join('home', os.path.sep, 'python')
'/python'

我知道 os.path.join() 会隐式插入目录分隔符。

os.path.sep有什么用？为什么会截断路径？

Answer 1

Where os.path.sep is usefull?

我怀疑它存在的主要原因是模块中无论如何都需要像这样的变量（以避免硬编码），如果它存在，它也可能被记录下来。它的文档说它是 "occasionally useful".

Why it truncates the path?

来自docs for os.path.join()：

If a component is an absolute path, all previous components are thrown away and joining continues from the absolute path component.

和 / 是 *nix 系统上的绝对路径。

Answer 2

从 os.path.join() 通话中删除 os.path.sep。 os.path.join() 在内部使用 os.path.sep。

在您的系统上，os.path.sep == '/' 被解释为根目录（绝对路径），因此 os.path.join('home', '/', 'python') 等同于 os.path.join('/', 'python') == '/python'。 From the docs:

If a component is an absolute path, all previous components are thrown away and joining continues from the absolute path component.

Answer 3

如 os.path.join -

的文档字符串中正确给出

Join two or more pathname components, inserting '/' as needed. If any component is an absolute path, all previous path components will be discarded.

docs中也给出了相同的-

os.path.join(path, *paths)

Join one or more path components intelligently. The return value is the concatenation of path and any members of *paths with exactly one directory separator (os.sep) following each non-empty part except the last, meaning that the result will only end in a separator if the last part is empty. If a component is an absolute path, all previous components are thrown away and joining continues from the absolute path component.

当你单独给出 os.path.sep 时，它被认为是根目录的绝对路径 - / .

请注意，这是基于 unix/linux 的 os.path，内部是 posixpath。尽管在 windows os.path.join() .

中可以看到相同的行为

例子-

>>> import os.path
>>> os.path.join.__doc__
"Join two or more pathname components, inserting '/' as needed.\n    If any component is an absolute path, all previous path components\n    will be discarded."

Answer 4

如果您在 POSIX 机器上，这是运行的代码片段：

posixpath.py

# Join pathnames.
# Ignore the previous parts if a part is absolute.
# Insert a '/' unless the first part is empty or already ends in '/'.

def join(a, *p):
    """Join two or more pathname components, inserting '/' as needed.
    If any component is an absolute path, all previous path components
    will be discarded.  An empty last part will result in a path that
    ends with a separator."""
    sep = _get_sep(a)
    path = a
    try:
        if not p:
            path[:0] + sep  #23780: Ensure compatible data type even if p is null.
        for b in p:
            if b.startswith(sep):
                path = b
            elif not path or path.endswith(sep):
                path += b
            else:
                path += sep + b
    except (TypeError, AttributeError, BytesWarning):
        genericpath._check_arg_types('join', a, *p)
        raise
    return path

具体来说，行：

        if b.startswith(sep):
            path = b

而且，由于 os.path.sep 肯定是从这个字符开始的，所以每当我们遇到它时，我们都会丢弃变量 path 中已经构造的部分，并从 [ 中的下一个元素重新开始=15=].

Answer 5

But when os.path.sep is used in os.path.join() , why it truncates the path?

直接引用os.path.join

的文档

If a component is an absolute path, all previous components are thrown away and joining continues from the absolute path component.

所以当你这样做时：

os.path.join('home', os.path.sep, 'python')

os.path.sep returns '/' 这是一个绝对路径，所以 'home' 被丢弃，你只得到 '/python' 作为输出。

从例子中也可以看出：

>>> import os
>>> os.path.join('home','/python','kivy')
'/python/kivy'

Where os.path.sep is usefull?

os.path.sep 或 os.sep returns 操作系统用来分隔路径名组件的字符。但再次引用 docs:

Note that knowing this is not sufficient to be able to parse or concatenate pathnames — use os.path.split() and os.path.join() — but it is occasionally useful.

How/where 要使用 os.path.sep？

How/where to use os.path.sep?

python

os.path