您如何找到路径的第一个元素？

Question

I just downloaded Python 3.4 and I'm wondering how you would go about finding the first directory of a relative path? Ie given the path a/b/c/d I would like to print a .

The closest I've gotten is:

from pathlib import Path
print(list(Path('a/b/c/d').parents)[-2])

or

p = Path('a/b/c/d')
print(p.parents[len(p.parents) - 2])

in both cases the -2 part is a bit magical. I've read the docs and the PEP, and haven't found any better way.. did I miss something obvious?

Answer 1

Use parts attribute:

>>> from pathlib import Path
>>> Path('a/b/c/d').parts
('a', 'b', 'c', 'd')
>>> Path('a/b/c/d').parts[0]
'a'

Answer 2

Path.parts is what you need.

p = Path("a/b/c/d")
print(p.parts[0])

Answer 3

From the documentation , parents gives you an immutable sequence providing access to the logical ancestors of the path ; the last element of that sequence would be the logical root, and the second to last element would then be the first directory in the path, which is what you're looking for. That is why you need to use the p.parents[len(p.parents)-2] shortcut ('-2' is for the 'second to last' element of a list).

Note that parents always gives you full formed paths. If you only want the directory name you might want to use p.parts instead. In that case the first element is the logical root, so you'd want p.parts[1] .