vistir: Setup / utilities which most projects eventually need

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🐉 Installation

Install from PyPI:

$ pipenv install vistir

Install from Github:

$ pipenv install -e git+https://github.com/sarugaku/vistir.git#egg=vistir

🐉 Summary

vistir is a library full of utility functions designed to make life easier. Here are some of the places where these functions are used:

🐉 Usage

Importing a utility

You can import utilities directly from vistir:

from vistir import cd
cd('/path/to/somedir'):
    do_stuff_in('somedir')

🐉 Functionality

vistir provides several categories of functionality, including:

  • Backports
  • Compatibility Shims
  • Context Managers
  • Miscellaneous Utilities
  • Path Utilities

Note

The backports should be imported via compat which will provide the native versions of the backported items if possible.

🐉 Compatibility Shims

Shims are provided for full API compatibility from python 2.7 through 3.7 for the following:

The following additional function is provided for encoding strings to the filesystem defualt encoding:

🐉 Context Managers

vistir provides the following context managers as utility contexts:

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)

replaced_stream

A context manager to temporarily swap out stream_name with a stream wrapper. This will capture the stream output and prevent it from being written as normal.

>>> orig_stdout = sys.stdout
>>> with replaced_stream("stdout") as stdout:
...     sys.stdout.write("hello")
...     assert stdout.getvalue() == "hello"

>>> sys.stdout.write("hello")
'hello'

replaced_streams

Temporarily replaces both sys.stdout and sys.stderr and captures anything written to these respective targets.

>>> import sys
>>> with vistir.contextmanagers.replaced_streams() as streams:
>>>     stdout, stderr = streams
>>>     sys.stderr.write("test")
>>>     sys.stdout.write("hello")
>>>     assert stdout.getvalue() == "hello"
>>>     assert stderr.getvalue() == "test"

>>> stdout.getvalue()
'hello'

>>> stderr.getvalue()
'test'

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']

🐉 Miscellaneous Utilities

The following Miscellaneous utilities are available as helper methods:

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.org/simple")
>>> new_source = source(name="pypi")
>>> new_source
<__main__.Source object at 0x7f23af189b38>
>>> new_source.__dict__
{'url': 'https://pypi.org/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'

chunked

Splits an iterable up into groups of the specified length, per more itertools. Returns an iterable.

This example will create groups of chunk size 5, which means there will be 6 groups.

>>> chunked_iterable = vistir.misc.chunked(5, range(30))
>>> for chunk in chunked_iterable:
...     add_to_some_queue(chunk)

take

Take elements from the supplied iterable without consuming it.

>>> iterable = range(30)
>>> first_10 = take(10, iterable)
>>> [i for i in first_10]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> [i for i in iterable]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

divide

Splits an iterable up into the specified number of groups, per more itertools. Returns an iterable.

>>> iterable = range(30)
>>> groups = []
>>> for grp in vistir.misc.divide(3, iterable):
...     groups.append(grp)
>>> groups
[<tuple_iterator object at 0x7fb7966006a0>, <tuple_iterator object at 0x7fb796652780>, <tuple_iterator object at 0x7fb79650a2b0>]

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.

>>> vistir.misc.decode_for_output(u"Some text")
"some default locale encoded text"

get_canonical_encoding_name

Given an encoding name, get the canonical name from a codec lookup.

>>> vistir.misc.get_canonical_encoding_name("utf8")
"utf-8"

get_wrapped_stream

Given a stream, wrap it in a StreamWrapper instance and return the wrapped stream.

>>> stream = sys.stdout
>>> wrapped_stream = vistir.misc.get_wrapped_stream(sys.stdout)

StreamWrapper

A stream wrapper and compatibility class for handling wrapping file-like stream objects which may be used in place of sys.stdout and other streams.

>>> wrapped_stream = vistir.misc.StreamWrapper(sys.stdout, encoding="utf-8", errors="replace", line_buffering=True)
>>> wrapped_stream = vistir.misc.StreamWrapper(io.StringIO(), encoding="utf-8", errors="replace", line_buffering=True)

get_text_stream

An implementation of the StreamWrapper for the purpose of wrapping sys.stdin or sys.stdout.

On Windows, this returns the appropriate handle to the requested output stream.

>>> text_stream = vistir.misc.get_text_stream("stdout")
>>> sys.stdout = text_stream
>>> sys.stdin = vistir.misc.get_text_stream("stdin")
>>> vistir.misc.echo(u"\0499", fg="green")
ҙ

replace_with_text_stream

Given a text stream name, replaces the text stream with a StreamWrapper instance.

>>> vistir.misc.replace_with_text_stream("stdout")

Once invoked, the standard stream in question is replaced with the required wrapper, turning it into a TextIOWrapper compatible stream (which ensures that unicode characters can be written to it).

get_text_stdin

A helper function for calling get_text_stream(“stdin”).

get_text_stdout

A helper function for calling get_text_stream(“stdout”).

get_text_stderr

A helper function for calling get_text_stream(“stderr”).

echo

Writes colored, stream-compatible output to the desired handle (sys.stdout by default).

>>> vistir.misc.echo("some text", fg="green", bg="black", style="bold", err=True)  # write to stderr
some text
>>> vistir.misc.echo("some other text", fg="cyan", bg="white", style="underline")  # write to stdout
some other text

🐉 Path Utilities

vistir provides utilities for interacting with filesystem paths:

normalize_path

Return a case-normalized absolute variable-expanded path.

>>> vistir.path.normalize_path("~/${USER}")
/home/user/user

is_in_path

Determine if the provided full path is in the given parent root.

>>> vistir.path.is_in_path("~/.pyenv/versions/3.7.1/bin/python", "${PYENV_ROOT}/versions")
True

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 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 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]
[]

Note

Setting ignore_errors=True may cause this to silently fail to delete the path

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'