vistir 0.2.3

atomic_open_for_write

This context manager ensures that a file only gets overwritten if the contents can be successfully written in its place. If you open a file for writing and then fail in the middle under normal circumstances, your original file is already gone.

>>> fn = "test_file.txt"
>>> with open(fn, "w") as fh:
        fh.write("this is some test text")
>>> read_test_file()
this is some test text
>>> def raise_exception_while_writing(filename):
        with vistir.contextmanagers.atomic_open_for_write(filename) as fh:
            fh.write("Overwriting all the text from before with even newer text")
            raise RuntimeError("But did it get overwritten now?")
>>> raise_exception_while_writing(fn)
    Traceback (most recent call last):
        ...
    RuntimeError: But did it get overwritten now?
>>> read_test_file()
    writing some new text

cd

A context manager for temporarily changing the working directory.

>>> os.path.abspath(os.curdir)
'/tmp/test'
>>> with vistir.contextmanagers.cd('/tmp/vistir_test'):
        print(os.path.abspath(os.curdir))
/tmp/vistir_test

open_file

A context manager for streaming file contents, either local or remote. It is recommended to pair this with an iterator which employs a sensible chunk size.

>>> filecontents = b""
    with vistir.contextmanagers.open_file("https://norvig.com/big.txt") as fp:
        for chunk in iter(lambda: fp.read(16384), b""):
            filecontents.append(chunk)
>>> import io
>>> import shutil
>>> filecontents = io.BytesIO(b"")
>>> with vistir.contextmanagers.open_file("https://norvig.com/big.txt") as fp:
        shutil.copyfileobj(fp, filecontents)

spinner

A context manager for wrapping some actions with a threaded, interrupt-safe spinner. The spinner is fully compatible with all terminals (you can use bouncingBar on non-utf8 terminals) and will allow you to update the text of the spinner itself by simply setting spinner.text or write lines to the screen above the spinner by using spinner.write(line). Success text can be indicated using spinner.ok("Text") and failure text can be indicated with spinner.fail("Fail text").

>>> lines = ["a", "b"]
>>> with vistir.contextmanagers.spinner(spinner_name="dots", text="Running...", handler_map={}, nospin=False) as sp:
        for line in lines:
        sp.write(line + "\n")
        while some_variable = some_queue.pop():
            sp.text = "Consuming item: %s" % some_variable
        if success_condition:
            sp.ok("Succeeded!")
        else:
            sp.fail("Failed!")

temp_environ

Sets a temporary environment context to freely manipulate os.environ which will be reset upon exiting the context.

>>> os.environ['MY_KEY'] = "test"
>>> os.environ['MY_KEY']
'test'
>>> with vistir.contextmanagers.temp_environ():
        os.environ['MY_KEY'] = "another thing"
        print("New key: %s" % os.environ['MY_KEY'])
New key: another thing
>>> os.environ['MY_KEY']
'test'

temp_path

Sets a temporary environment context to freely manipulate sys.path which will be reset upon exiting the context.

>>> path_from_virtualenv = load_path("/path/to/venv/bin/python")
>>> print(sys.path)
['/home/user/.pyenv/versions/3.7.0/bin', '/home/user/.pyenv/versions/3.7.0/lib/python37.zip', '/home/user/.pyenv/versions/3.7.0/lib/python3.7', '/home/user/.pyenv/versions/3.7.0/lib/python3.7/lib-dynload', '/home/user/.pyenv/versions/3.7.0/lib/python3.7/site-packages']
>>> with temp_path():
        sys.path = path_from_virtualenv
        # Running in the context of the path above
        run(["pip", "install", "stuff"])
>>> print(sys.path)
['/home/user/.pyenv/versions/3.7.0/bin', '/home/user/.pyenv/versions/3.7.0/lib/python37.zip', '/home/user/.pyenv/versions/3.7.0/lib/python3.7', '/home/user/.pyenv/versions/3.7.0/lib/python3.7/lib-dynload', '/home/user/.pyenv/versions/3.7.0/lib/python3.7/site-packages']

shell_escape

Escapes a string for use as shell input when passing shell=True to os.Popen.

>>> vistir.misc.shell_escape("/tmp/test/test script.py hello")
'/tmp/test/test script.py hello'

unnest

Unnests nested iterables into a flattened one.

>>> nested_iterable = (1234, (3456, 4398345, (234234)), (2396, (23895750, 9283798, 29384, (289375983275, 293759, 2347, (2098, 7987, 27599)))))
>>> list(vistir.misc.unnest(nested_iterable))
[1234, 3456, 4398345, 234234, 2396, 23895750, 9283798, 29384, 289375983275, 293759, 2347, 2098, 7987, 27599]

dedup

Deduplicates an iterable (like a set, but preserving order).

>>> iterable = ["repeatedval", "uniqueval", "repeatedval", "anotherval", "somethingelse"]
>>> list(vistir.misc.dedup(iterable))
['repeatedval', 'uniqueval', 'anotherval', 'somethingelse']

run

Runs the given command using subprocess.Popen and passing sane defaults.

>>> out, err = vistir.run(["cat", "/proc/version"])
>>> out
'Linux version 4.15.0-27-generic (buildd@lgw01-amd64-044) (gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3)) #29-Ubuntu SMP Wed Jul 11 08:21:57 UTC 2018'

load_path

Load the sys.path from the given python executable’s environment as json.

>>> load_path("/home/user/.virtualenvs/requirementslib-5MhGuG3C/bin/python")
['', '/home/user/.virtualenvs/requirementslib-5MhGuG3C/lib/python37.zip', '/home/user/.virtualenvs/requirementslib-5MhGuG3C/lib/python3.7', '/home/user/.virtualenvs/requirementslib-5MhGuG3C/lib/python3.7/lib-dynload', '/home/user/.pyenv/versions/3.7.0/lib/python3.7', '/home/user/.virtualenvs/requirementslib-5MhGuG3C/lib/python3.7/site-packages', '/home/user/git/requirementslib/src']

partialclass

Create a partially instantiated class.

>>> source = partialclass(Source, url="https://pypi-hypernode.com/simple")
>>> new_source = source(name="pypi")
>>> new_source
<__main__.Source object at 0x7f23af189b38>
>>> new_source.__dict__
{'url': 'https://pypi-hypernode.com/simple', 'verify_ssl': True, 'name': 'pypi'}

to_text

Convert arbitrary text-formattable input to text while handling errors.

>>> vistir.misc.to_text(b"these are bytes")
'these are bytes'

to_bytes

Converts arbitrary byte-convertable input to bytes while handling errors.

>>> vistir.misc.to_bytes("this is some text")
b'this is some text'
>>> vistir.misc.to_bytes(u"this is some text")
b'this is some text'

decode_for_output

Converts an arbitrary text input to output which is encoded for printing to terminal outputs using the system preferred locale using locale.getpreferredencoding(False) with some additional hackery on linux systems.

get_converted_relative_path

Convert the supplied path to a relative path (relative to os.curdir)

>>> os.chdir('/home/user/code/myrepo/myfolder')
>>> vistir.path.get_converted_relative_path('/home/user/code/file.zip')
'./../../file.zip'
>>> vistir.path.get_converted_relative_path('/home/user/code/myrepo/myfolder/mysubfolder')
'./mysubfolder'
>>> vistir.path.get_converted_relative_path('/home/user/code/myrepo/myfolder')
'.'

handle_remove_readonly

Error handler for shutil.rmtree.

Windows source repo folders are read-only by default, so this error handler attempts to set them as writeable and then proceed with deletion.

This function will call check vistir.path.is_readonly_path before attempting to call vistir.path.set_write_bit on the target path and try again.

is_file_url

Checks whether the given url is a properly formatted file:// uri.

>>> vistir.path.is_file_url('file:///home/user/somefile.zip')
True
>>> vistir.path.is_file_url('/home/user/somefile.zip')
False

is_readonly_path

Check if a provided path exists and is readonly by checking for bool(path.stat & stat.S_IREAD) and not os.access(path, os.W_OK)

>>> vistir.path.is_readonly_path('/etc/passwd')
True
>>> vistir.path.is_readonly_path('/home/user/.bashrc')
False

is_valid_url

Checks whether a URL is valid and parseable by checking for the presence of a scheme and a netloc.

>>> vistir.path.is_valid_url("https://google.com")
True
>>> vistir.path.is_valid_url("/home/user/somefile")
False

mkdir_p

Recursively creates the target directory and all of its parents if they do not already exist. Fails silently if they do.

>>> os.mkdir('/tmp/test_dir')
>>> os.listdir('/tmp/test_dir')
[]
>>> vistir.path.mkdir_p('/tmp/test_dir/child/subchild/subsubchild')
>>> os.listdir('/tmp/test_dir/child/subchild')
['subsubchild']

ensure_mkdir_p

A decorator which ensures that the caller function’s return value is created as a directory on the filesystem.

>>> @ensure_mkdir_p
def return_fake_value(path):
    return path
>>> return_fake_value('/tmp/test_dir')
>>> os.listdir('/tmp/test_dir')
[]
>>> return_fake_value('/tmp/test_dir/child/subchild/subsubchild')
>>> os.listdir('/tmp/test_dir/child/subchild')
['subsubchild']

create_tracked_tempdir

Creates a tracked temporary directory using vistir.path.TemporaryDirectory, but does not remove the directory when the return value goes out of scope, instead registers a handler to cleanup on program exit.

>>> temp_dir = vistir.path.create_tracked_tempdir(prefix="test_dir")
>>> assert temp_dir.startswith("test_dir")
True
>>> with vistir.path.create_tracked_tempdir(prefix="test_dir") as temp_dir:
    with io.open(os.path.join(temp_dir, "test_file.txt"), "w") as fh:
        fh.write("this is a test")
>>> os.listdir(temp_dir)

create_tracked_tempfile

Creates a tracked temporary file using vistir.compat.NamedTemporaryFile, but creates a weakref.finalize call which will detach on garbage collection to close and delete the file.

>>> temp_file = vistir.path.create_tracked_tempfile(prefix="requirements", suffix="txt")
>>> temp_file.write("some\nstuff")
>>> exit()

path_to_url

Convert the supplied local path to a file uri.

>>> path_to_url("/home/user/code/myrepo/myfile.zip")
'file:///home/user/code/myrepo/myfile.zip'

rmtree

Stand-in for shutil.rmtree with additional error-handling.

This version of rmtree handles read-only paths, especially in the case of index files written by certain source control systems.

>>> vistir.path.rmtree('/tmp/test_dir')
>>> [d for d in os.listdir('/tmp') if 'test_dir' in d]
[]

safe_expandvars

Call os.path.expandvars if value is a string, otherwise do nothing.

>>> os.environ['TEST_VAR'] = "MY_TEST_VALUE"
>>> vistir.path.safe_expandvars("https://myuser:${TEST_VAR}@myfakewebsite.com")
'https://myuser:MY_TEST_VALUE@myfakewebsite.com'

set_write_bit

Set read-write permissions for the current user on the target path. Fail silently if the path doesn’t exist.

>>> vistir.path.set_write_bit('/path/to/some/file')
>>> with open('/path/to/some/file', 'w') as fh:
        fh.write("test text!")

url_to_path

Convert a valid file url to a local filesystem path. Follows logic taken from pip.

>>> vistir.path.url_to_path("file:///home/user/somefile.zip")
'/home/user/somefile.zip'