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Comment by taylorfausak | Hacker News Reader

Wow, I haven't heard of pathlib [1] before now, but it looks awesome! In particular, using the slash operator to join paths is brilliant.

    >>> p = PurePath('/etc')
    >>> p / 'init.d' / 'apache2'
    PurePosixPath('/etc/init.d/apache2')

[1]: http://docs.python.org/3.4/library/pathlib.html

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Scala does something similarly neat with using #| for piping system commands.

Slash for Scala is not used by default though for path joining, but it can be by adding an implicit function:

  implicit def slash(str: String) = new { def /(joinStr: String) = str + java.io.File.separatorChar + joinStr} 

  val joinedStr = "abc"/"def"/"ghi"
  > joinedStr : java.lang.String = abc/def/ghi

Shell friendly syntax can be used for stdin/stdout in Scala as well (already in the stdlib with no implicits required):

#< Redirect STDIN

#> Redirect STDOUT

#>> Append to STDOUT

#&& Create an AND list

#!! Create an OR list

http://stackoverflow.com/questions/12772605/scala-shell-comm...

http://alvinalexander.com/scala/scala-execute-exec-external-...

There are Plumbum shell combinators in Python http://plumbum.readthedocs.org/en/latest/

There are a couple of modules that do this kind of thing but Plumbum looks interesting, particularly

http://plumbum.readthedocs.org/en/latest/local_commands.html...

>from plumbum.cmd import cat

>>cat('tmp.txt') #invokes cat tmp.txt on the system

I hadn't heard of it either, although I have played with Twisted's FilePath[1] class previously.

I didn't really understand the attraction of an OO filesystem API until I actually used it in anger and realised how handy it was that all the relevant functions were on the object I was messing with, instead of arbitrarily divided between the "os" and "os.path" modules.

Some (hopefully constructive) suggestions for the pathlib API:

- Python 3 dicts ditched .iterkeys(), .itervalues() and .iteritems(); why does pathlib use the clumsy .iterdir() when it could just be called .children?

- Like many Python programmers (I assume), I'm more familiar with POSIX command-line tools than I am with POSIX APIs. Command-line tools generally have an option to control whether they dereference symlinks (cp -L, find -L, etc) rather than having a separate. parallel tool that does the same thing. I think it would be neater if .lstat() and .lchmod() were removed in favour of a "follow_symlinks" parameter to .stat() and .chmod() (and .is_dir() and .touch() and .owner(), and, and, and..)

- If you're going to have convenience functions that pick out interesting bits from the .stat() return value, I would find .size() far more practical than .is_socket()

[1]: http://twistedmatrix.com/documents/current/api/twisted.pytho...

One of the many things I like about Python is their pragmatic approach to operator overloading. Well, their pragmatic approach to everything, really.

FWIW, the boost::filesystem C++ package uses the / operator in the same way

No one objected to using "pure" instead of the more common "abstract" (which is the actual antonym of "concrete") ?? Why do people do this?

Concrete paths inherit from pure paths - this would be quite strange using antonyms. This isn't like an "abstract" base class. It's a full class on its own, which is extended by another.

Anyway, I think it's meant to be "pure" like pure functions, generally having no side effects or external inputs.

https://en.wikipedia.org/wiki/Pure_function

i think so too. like it says in the docs: "Regardless of the system you’re running on, you can instantiate all of these classes, since they don’t provide any operation that does system calls." http://docs.python.org/3.4/library/pathlib.html#pure-paths

The precursor path library [1] by J. Orendorff had the slash operator overloading trick a decade (or more) ago.

[1] https://pypi.python.org/pypi/path.py/1.2

I thought operator overloading like that was considered bad practise. It seems to me that the + operator should have been overloaded, not the / operator.

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