Source code for vistir.contextmanagers

# -*- coding=utf-8 -*-
from __future__ import absolute_import, print_function, unicode_literals

import io
import os
import stat
import sys
from contextlib import closing, contextmanager

import six

from .compat import IS_TYPE_CHECKING, NamedTemporaryFile, Path
from .path import is_file_url, is_valid_url, path_to_url, url_to_path

    from typing import (
    from types import ModuleType
    from requests import Session
    from six.moves.http_client import HTTPResponse as Urllib_HTTPResponse
    from urllib3.response import HTTPResponse as Urllib3_HTTPResponse
    from .spin import VistirSpinner, DummySpinner

    TSpinner = Union[VistirSpinner, DummySpinner]
    _T = TypeVar("_T")

__all__ = [

# Borrowed from Pew.
# See
[docs]@contextmanager def temp_environ(): # type: () -> Iterator[None] """Allow the ability to set os.environ temporarily""" environ = dict(os.environ) try: yield finally: os.environ.clear() os.environ.update(environ)
[docs]@contextmanager def temp_path(): # type: () -> Iterator[None] """A context manager which allows the ability to set sys.path temporarily >>> 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/', '/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/', '/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' ] """ path = [p for p in sys.path] try: yield finally: sys.path = [p for p in path]
[docs]@contextmanager def cd(path): # type: () -> Iterator[None] """Context manager to temporarily change working directories :param str path: The directory to move into >>> print(os.path.abspath(os.curdir)) '/home/user/code/myrepo' >>> with cd("/home/user/code/otherdir/subdir"): ... print("Changed directory: %s" % os.path.abspath(os.curdir)) Changed directory: /home/user/code/otherdir/subdir >>> print(os.path.abspath(os.curdir)) '/home/user/code/myrepo' """ if not path: return prev_cwd = Path.cwd().as_posix() if isinstance(path, Path): path = path.as_posix() os.chdir(str(path)) try: yield finally: os.chdir(prev_cwd)
[docs]@contextmanager def dummy_spinner(spin_type, text, **kwargs): # type: (str, str, Any) class FakeClass(object): def __init__(self, text=""): self.text = text def fail(self, exitcode=1, text=None): if text: print(text) raise SystemExit(exitcode, text) def ok(self, text): print(text) return 0 def write(self, text): print(text) myobj = FakeClass(text) yield myobj
[docs]@contextmanager def spinner( spinner_name=None, # type: Optional[str] start_text=None, # type: Optional[str] handler_map=None, # type: Optional[Dict[str, Callable]] nospin=False, # type: bool write_to_stdout=True, # type: bool ): # type: (...) -> ContextManager[TSpinner] """Get a spinner object or a dummy spinner to wrap a context. :param str spinner_name: A spinner type e.g. "dots" or "bouncingBar" (default: {"bouncingBar"}) :param str start_text: Text to start off the spinner with (default: {None}) :param dict handler_map: Handler map for signals to be handled gracefully (default: {None}) :param bool nospin: If true, use the dummy spinner (default: {False}) :param bool write_to_stdout: Writes to stdout if true, otherwise writes to stderr (default: True) :return: A spinner object which can be manipulated while alive :rtype: :class:`~vistir.spin.VistirSpinner` Raises: RuntimeError -- Raised if the spinner extra is not installed """ from .spin import create_spinner has_yaspin = None try: import yaspin except ImportError: has_yaspin = False if not nospin: raise RuntimeError( "Failed to import spinner! Reinstall vistir with command:" " pip install --upgrade vistir[spinner]" ) else: spinner_name = "" else: has_yaspin = True spinner_name = "" use_yaspin = (has_yaspin is False) or (nospin is True) if has_yaspin is None or has_yaspin is True and not nospin: use_yaspin = True if start_text is None and use_yaspin is True: start_text = "Running..." with create_spinner( spinner_name=spinner_name, text=start_text, handler_map=handler_map, nospin=nospin, use_yaspin=use_yaspin, write_to_stdout=write_to_stdout, ) as _spinner: yield _spinner
[docs]@contextmanager def atomic_open_for_write(target, binary=False, newline=None, encoding=None): # type: (str, bool, Optional[str], Optional[str]) -> None """Atomically open `target` for writing. This is based on Lektor's `atomic_open()` utility, but simplified a lot to handle only writing, and skip many multi-process/thread edge cases handled by Werkzeug. :param str target: Target filename to write :param bool binary: Whether to open in binary mode, default False :param Optional[str] newline: The newline character to use when writing, determined from system if not supplied. :param Optional[str] encoding: The encoding to use when writing, defaults to system encoding. How this works: * Create a temp file (in the same directory of the actual target), and yield for surrounding code to write to it. * If some thing goes wrong, try to remove the temp file. The actual target is not touched whatsoever. * If everything goes well, close the temp file, and replace the actual target with this new file. .. code:: python >>> fn = "test_file.txt" >>> def read_test_file(filename=fn): with open(filename, 'r') as fh: print( >>> 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 open(filename, "w") as fh: fh.write("writing some new text") raise RuntimeError("Uh oh, hope your file didn't get overwritten") >>> raise_exception_while_writing(fn) Traceback (most recent call last): ... RuntimeError: Uh oh, hope your file didn't get overwritten >>> read_test_file() writing some new text # Now try with vistir >>> 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 """ mode = "w+b" if binary else "w" f = NamedTemporaryFile( dir=os.path.dirname(target), prefix=".__atomic-write", mode=mode, encoding=encoding, newline=newline, delete=False, ) # set permissions to 0644 try: os.chmod(, stat.S_IWUSR | stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH) except OSError: pass try: yield f except BaseException: f.close() try: os.remove( except OSError: pass raise else: f.close() try: os.remove(target) # This is needed on Windows. except OSError: pass os.rename(, target) # No os.replace() on Python 2.
[docs]@contextmanager def open_file( link, # type: Union[_T, str] session=None, # type: Optional[Session] stream=True, # type: bool ): # type: (...) -> ContextManager[Union[IO[bytes], Urllib3_HTTPResponse, Urllib_HTTPResponse]] """ Open local or remote file for reading. :param pip._internal.index.Link link: A link object from resolving dependencies with pip, or else a URL. :param Optional[Session] session: A :class:`~requests.Session` instance :param bool stream: Whether to stream the content if remote, default True :raises ValueError: If link points to a local directory. :return: a context manager to the opened file-like object """ if not isinstance(link, six.string_types): try: link = link.url_without_fragment except AttributeError: raise ValueError("Cannot parse url from unkown type: {0!r}".format(link)) if not is_valid_url(link) and os.path.exists(link): link = path_to_url(link) if is_file_url(link): # Local URL local_path = url_to_path(link) if os.path.isdir(local_path): raise ValueError("Cannot open directory for read: {}".format(link)) else: with, "rb") as local_file: yield local_file else: # Remote URL headers = {"Accept-Encoding": "identity"} if not session: try: from requests import Session # noqa except ImportError: session = None else: session = Session() if session is None: with closing(six.moves.urllib.request.urlopen(link)) as f: yield f else: with session.get(link, headers=headers, stream=stream) as resp: try: raw = getattr(resp, "raw", None) result = raw if raw else resp yield result finally: if raw: conn = raw._connection if conn is not None: conn.close() result.close()
[docs]@contextmanager def replaced_stream(stream_name): # type: (str) -> Iterator[IO[Text]] """ Context manager to temporarily swap out *stream_name* with a stream wrapper. :param str stream_name: The name of a sys stream to wrap :returns: A ``StreamWrapper`` replacement, temporarily >>> orig_stdout = sys.stdout >>> with replaced_stream("stdout") as stdout: ... sys.stdout.write("hello") ... assert stdout.getvalue() == "hello" >>> sys.stdout.write("hello") 'hello' """ orig_stream = getattr(sys, stream_name) new_stream = six.StringIO() try: setattr(sys, stream_name, new_stream) yield getattr(sys, stream_name) finally: setattr(sys, stream_name, orig_stream)
[docs]@contextmanager def replaced_streams(): # type: () -> Iterator[Tuple[IO[Text], IO[Text]]] """ Context manager to replace both ``sys.stdout`` and ``sys.stderr`` using ``replaced_stream`` returns: *(stdout, stderr)* >>> 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' """ with replaced_stream("stdout") as stdout: with replaced_stream("stderr") as stderr: yield (stdout, stderr)