Python pathlib.Path - how do I get just a platform independent file separator as a string?

Question

I am creating a format string that is different based on class, that is used to generate a filename by a generic class method. I'm using the Python 3.4+ pathlib.Path module for object-oriented file I/O.

In building this string, the path separator is missing, and rather than just put the windows version in, I want to add a platform independent file separator.

I searched the pathlib docs, and answers here about this, but all the examples assume I'm building a Path object, not a string. The pathlib functions will add the correct separator in any string outputs, but those are actual paths - so it won't work.

Besides something hacky like writing a string and parsing it to figure out what the separator is, is there a way to directly get the current, correct file separator string?

Prefer an answer using pathlib.Path, rather than os or shutil packages.

Here's what the code looks like:

In the constructor:

    self.outputdir = Path('drive:\\dir\\file')
    self.indiv_fileformatstr = str(self.outputdir) + '{}_new.m'

In the final method used:

    indiv_filename = Path(self.indiv_fileformatstr.format(topic))

This leaves out the file separator

Answer 1

There is nothing public in the pathlib module providing the character used by the operating system to separate pathname components. If you really need it, import os and use os.sep .

But you likely don't need it in the first place - it's missing the point of pathlib if you convert to strings in order to join a filename. In typical usage, the separator string itself isn't used for concatenating path components because pathlib overrides division operators ( __truediv__ and __rtruediv__ ) for this purpose. Similarly, it's not needed for splitting due to methods such as Path.parts .

Instead of:

self.indiv_fileformatstr = str(self.outputdir) + '{}_new.m'

You would usually do something like:

self.indiv_fileformatpath = self.outputdir / '{}_new.m'
self.indiv_fileformatstr = str(self.indiv_fileformatpath)

Answer 2

The platform-independent separator is in pathlib.os.sep

Answer 3

Solution using wim's answer

Based on wim's answer, the following works great:

1. Save the format string in the Path object
2. When needing to substitute into the templated filename in the future, just use str(path_object) to get the string back out.

import pathlib

# Start with following, with self.outputdir as pathlib.Path object
outputdir = 'c:\\myfolder'
file_template_path = outputdir / '{}_new.m'

# Then to make the final file object later (i.e. in a child class, etc.)
base_filename_string = 'myfile'
new_file = pathlib.Path(str(file_template).format(base_filename_string))

This creates:

pathlib.Path("c:\\myfolder\myfile_new.m")

Creating the template with prefix/postfix/etc.

If you need to apply other variables, you can use 2 levels of formatting to apply specialized prefixes/postfixes, etc., then store the final template in a Path object, as shown above.

When creating 2 levels of formatting, use double brackets where the first level formatter should just create a single bracket and not try to interpret a tag. ie {{basename}} becomes just {basename} without any variable substitution.

prefix = 'new_'
postfix = '_1'
ext = 'txt'
file_template_path = outputdir / f'{prefix}{{}}{postfix}.{ext}'

which becomes a path object with the following string:

$ file_template_path
pathlib.Path("c:\\myfolder\new_{}_1.txt")