Source code for franz.openrdf.util.contexts
################################################################################
# Copyright (c) 2006-2017 Franz Inc.
# All rights reserved. This program and the accompanying materials are
# made available under the terms of the MIT License which accompanies
# this distribution, and is available at http://opensource.org/licenses/MIT
################################################################################
"""
Utilities related to context managers.
"""
from contextlib import contextmanager
import os
import sys
from past.builtins import basestring
[docs]@contextmanager
def wrap_context(value):
"""
Wrap a no-op context around an arbitrary value, so that it can be
used in a ``with`` statement.
:param value: Value to be returned by the context manager.
:return: A context manager wrapping ``value``.
"""
yield value
[docs]@contextmanager
def output_to(target):
"""
Returns a file-like object constructed from target.
Target can be:
- None: the returned stream will ignore all data
- True: data will be written to stdout.
- a string: a file will be opened (in binary mode)
- a file-like object: will be returned as is.
- an int - a file descriptor.
:param target: File path, None or a file-like object.
"""
if target is None:
# TODO: consider replacing with an object with empty methods
target = os.devnull
# Note that True is also an int (and it equals 1 = stdout),
# but we give it a special treatment because our doctests
# are not smart enough to capture things written to an fd.
if target is True:
# Make sure that the thing we return supports binary I/O
if hasattr(sys.stdout, 'buffer'):
yield sys.stdout.buffer
else:
yield sys.stdout
elif isinstance(target, int):
with os.fdopen(target, 'wb') as out:
yield out
elif isinstance(target, basestring):
with open(target, 'wb') as out:
yield out
elif hasattr(target, 'write'):
# If it quacks like a duck and has a write method...
yield target
else:
raise ValueError('Invalid output specification %s' % target)