Mercurial > hg
view contrib/python-zstandard/zstandard/__init__.py @ 48875:6000f5b25c9b
py2: remove simple from __future__ statements
These were needed for Python 2 support. Now that our linter no longer
mandates these, we can start deleting them.
Differential Revision: https://phab.mercurial-scm.org/D12254
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Thu, 03 Mar 2022 17:34:00 +0100 |
parents | de7838053207 |
children |
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# Copyright (c) 2017-present, Gregory Szorc # All rights reserved. # # This software may be modified and distributed under the terms # of the BSD license. See the LICENSE file for details. """Python interface to the Zstandard (zstd) compression library.""" # This module serves 2 roles: # # 1) Export the C or CFFI "backend" through a central module. # 2) Implement additional functionality built on top of C or CFFI backend. import os import platform # Some Python implementations don't support C extensions. That's why we have # a CFFI implementation in the first place. The code here import one of our # "backends" then re-exports the symbols from this module. For convenience, # we support falling back to the CFFI backend if the C extension can't be # imported. But for performance reasons, we only do this on unknown Python # implementation. Notably, for CPython we require the C extension by default. # Because someone will inevitably want special behavior, the behavior is # configurable via an environment variable. A potentially better way to handle # this is to import a special ``__importpolicy__`` module or something # defining a variable and `setup.py` could write the file with whatever # policy was specified at build time. Until someone needs it, we go with # the hacky but simple environment variable approach. _module_policy = os.environ.get("PYTHON_ZSTANDARD_IMPORT_POLICY", "default") if _module_policy == "default": if platform.python_implementation() in ("CPython",): from zstd import * backend = "cext" elif platform.python_implementation() in ("PyPy",): from .cffi import * backend = "cffi" else: try: from zstd import * backend = "cext" except ImportError: from .cffi import * backend = "cffi" elif _module_policy == "cffi_fallback": try: from zstd import * backend = "cext" except ImportError: from .cffi import * backend = "cffi" elif _module_policy == "cext": from zstd import * backend = "cext" elif _module_policy == "cffi": from .cffi import * backend = "cffi" else: raise ImportError( "unknown module import policy: %s; use default, cffi_fallback, " "cext, or cffi" % _module_policy ) # Keep this in sync with python-zstandard.h. __version__ = "0.13.0"