cachepath 1.1.1
Pythonic parameterized cache paths.
License: MIT license
Keywords: cachepath,paths,pathlib,cache,temp

Welcome to cachepath's documentation!
======================================

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        :alt: Documentation Status

A small package for pythonic parameterized cache paths.

Getting Started
----------------

**Install:** ``pip install cachepath``

**Import:** ``from cachepath import CachePath, TempPath, Path``

**Docs:** `ReadTheDocs`_ | `API doc is here`_

**Why?**
    1. Integrates ``pathlib`` with ``tempfile.gettempdir`` and ``shutil.rmtree`` by providing ``TempPath`` and ``Path.rm()``::

          path = TempPath()
          path.rm()
          # or would you rather..
          path = None
          with tempfile.NamedTemporaryFile(delete=False) as f:
              path = Path(f.name)
          # Only now can we use Path. If we tried using it within the With
          # (for example for path.read_text()), we'd break on Windows
          path.unlink()  # only if file, doesn't work on folders

    2. Wraps ``pathlib`` import for Py2/3 compat. (not in ``six``!)::

          from cachepath import Path
          # or
          try: from pathlib import Path; except ImportError: from pathlib2 import Path

    3. Provides `CachePath`_, which lets you quickly get a parameterized temp filename, with all folders automatically created::

          r = CachePath(date, userid, 'expensive_results.txt')
          assert (r == Path('/tmp/', date, userid, 'expensive_results.txt')
                  and r.parent.exists())
          r.rm()  # File remove
          r.parent.rm()  # Symmetric with folder remove!

          # Without cachepath
          p = Path(tempfile.gettempdir(), date, userid, 'expensive_results.txt').
          # Don't update timestamp if it already exists so that we don't cause
          # Make-like tools to always think something's changed
          if not p.parent.exists():
              p.parent.mkdir(parents=True, exist_ok=True)

          p.unlink()  # Why is it .unlink() instead of .remove()?
          # Why .remove and .unlink, but mkdir instead of createdir?
          p.parent.remove()
          # .remove() might throw because there was another file in the folder,
          # but we didn't care, they're tempfiles!
          import shutil
          shutil.rmtree(p.parent)

**Why, but longer:**

Do you need a temp path to pass to some random tool for its logfile?
Behold, a gaping hole in ``pathlib``::

    import tempfile
    import os
    try: from pathlib import Path; except ImportError: from pathlib2 import Path
    def get_tempfile():
        fd, loc = tempfile.mkstemp()
        os.close(fd)  # If we forgot do this, it would stay open until process exit
        return Path(loc)

    # Easier way
    from cachepath import TempPath
    def get_tempfile():
        return TempPath()  # Path('/tmp/213kjdsrandom')


But this module is called cachepath, not temppath, what gives?

Suppose I'm running that same imaginary tool pretty often, but I'd like to skip running
it if I already have results for a certain day. Just sticking some identifying info into a filename
should be good enough.
Something like ``Path('/tmp/20181204_toolresults.txt')`` ::

    # try: from pathlib import Path; except ImportError: from pathlib2 import Path
    # We'll cheat a little to get py2/3 compat without so much ugliness
    from cachepath import Path
    import tempfile
    def get_tempfile(date):
        filename = '{}_toolresults.txt'.format(date)
        return Path(tempfile.gettempdir(), filename)

    # Easier to do this...
    from cachepath import CachePath
    def get_tempfile(date):
        return CachePath(date, suffix='.txt')

Not bad, but not great. But our requirements changed, let's go a step further.

Now I'm running this tool *a lot*, over a tree of data that looks
like this::

    2018-12-23
        person1
        person2
    2018-12-24
        person1
    2018-12-25
        person1

I want my logs to be structured the same way.  How hard can it be? ::

    2018-12-23/
        person1_output.txt
        person2_output.txt
    2018-12-24/
        person1_output.txt
    2018-12-25/
        person1_output.txt

Let's find out::

    # Let's get the easy way out of the way first :)
    def get_path(date, person):
        return CachePath(date, person, suffix='_output.txt')
        # Automatically ensures /tmp/date/ exists when we create the CachePath!

    # Now the hard way
    def get_path(date, person):
        personfilename = '{p}_output.txt'.format(p=person)
        returning = Path(tempfile.gettempdir())/date/personfilename
        # Does this mkdir update the modified timestamp of the folders we're in?
        # Might matter if we're part of a larger toolset...
        returning.parent.mkdir(exist_ok=True, parents=True)
        return returning

Suppose we hadn't remembered to make the ``$date/`` folders. When we passed the
Path out to another tool, or tried to .open it,
we may have gotten a Permission Denied
error on Unix systems rather than the "File/Folder not found" you might expect.
With CachePath, this can't happen. Creating a CachePath implicitly creates all
of the preceding directories necessary for your file to exist.

Now, suppose we found a bug in this external tool we were using and we're going
to re-run it for a day.
How do we clear out that day's results so that we can be sure we're looking
at fresh output from the tool? Well, with CachePath, it's just::

  def easy_clear_date(date):
      CachePath(date).clear()  # rm -r /tmp/date/*

But if you don't have cachepath, you'll find that most Python libs play it
pretty safe when it comes to files. Path.remove() requires the folder to be empty,
and doesn't provide a way to empty the folder. Not to mention, what if our results
folders had special permissions, or was actually a symlink, and we had write access
but not delete? Oh well,
let's see what we can do::

  def hard_clear_date(date):
      # We happen to know that date is a folder and not a file (at least in our
      # current design), so we know we need some form of .remove() rather than
      # .unlink(). Unfortunately, pathlib doesn't offer one for folders with
      # files still in them. If you google how to do it, you will find plenty of
      # answers, one of which is a pure pathlib recursive solution! But we're lazy,
      # so lets bring in yet another module:
      p = Path(tempfile.gettempdir(), date)
      import shutil
      if p.exists():
          shutil.rmtree(p)
      p.mkdir(exist_ok=True, parents=True)
      # This still isn't exactly equivalent to CachePath.clear(), because we've
      # lost whatever permissions were set on the date folder, and if it were
      # actually a symlink to somewhere else, that's gone now.

Convinced yet? ``pip install cachepath`` or copy `the source`_ into your local
``utils.py`` (you know you have one.)

`API doc is here`_.


By the way, as a side effect of importing ``cachepath``, all Paths get the ability
to do ``rm()`` and ``clear()``.


Shameless Promo
----------------
Find yourself working with paths a lot in cmd-line tools? You might like
`invoke`_ and/or `magicinvoke`_!



.. [*] The source for CachePath can be downloaded from the `Github repo`_.

.. _Github repo: https://github.com/haydenflinner/cachepath
.. [*] This package was created with Cookiecutter_ and the `audreyr/cookiecutter-pypackage`_ project template.

.. _`the source`: https://github.com/haydenflinner/cachepath/blob/master/cachepath/__init__.py
.. _Cookiecutter: https://github.com/audreyr/cookiecutter
.. _`audreyr/cookiecutter-pypackage`: https://github.com/audreyr/cookiecutter-pypackage
.. _`invoke`: https://www.pyinvoke.org
.. _`magicinvoke`: https://magicinvoke.readthedocs.io/en/latest/
.. _`ReadTheDocs`: https://cachepath.readthedocs.io/en/latest/
.. _`API doc is here`: https://cachepath.readthedocs.io/en/latest/cachepath.html
.. _`CachePath`: https://cachepath.readthedocs.io/en/latest/cachepath.html#cachepath.CachePath


=======
History
=======

1.0.0 (2018-12-08)
------------------

* Big doc updates. 1.0.0 to symbolize SemVer adherence.

0.1.0 (2018-12-08)
------------------

* First release on PyPI. Adds CachePath, TempPath, Path.