Stop doctests polluting current dir with temporary files #264

At present, when you run any doctests temporary netCDF files are created in the current directory.

This is slightly tiresome, and could be avoided by dumping files to a temporary directory, like pytest does.

Unfortunately, adding specific code to do that in every module / docs-sourcefile could also be tiresome and intrusive.

in run-doctests

Possibly, a way to control this could be added to the run_doctests tool ?

• e.g., run by default in a temporary cwd -
• but that could affect doctest execution, and make some things difficult (e.g. importing local code) ??

using tempfile

instead of e.g. data.to_nc4('tmp.nc'),

import pathlib
import testfile

tempdir = pathlib.Path(testfile.TemporaryDirectory())
# ...
path = tempdir / "tmp.nc"
to_nc4(data, path)
result = from_nc4(path)

with a test utility

Or.. A utility to create a temp directory that will be consistently destroyed afterwards might be useful
(as opposed to tempdir which does not arrange for destruction).

# in <testutils.py>
import pathlib

class TempDir(pathlib.Path):
    def __init__(self):
        # self.context is deleted when self is deleted --> destroys directory
        self.context = tempfile.TemporaryDirectory()
        self.path_str = self.context.__enter__()
        self.path = pathlib.Path(self.dirpath_str)

# a single common per-import object
tempdir = TempDir()

# ... 
# in docstrings / docs
# Usage is generally shorter, and directory is removed on program exit
>>> from testutils import tempdir

...

>>> filepath = tempdir.path / "tmp.nc"
>>> to_nc4(data, filepath)
>>> result = from_nc4(filepath)