1 files changed, 45 insertions, 0 deletions
diff --git a/zmq/backend/__init__.py b/zmq/backend/__init__.py
new file mode 100644
index 0000000..7cac725
--- /dev/null
+++ b/zmq/backend/__init__.py
@@ -0,0 +1,45 @@
+"""Import basic exposure of libzmq C API as a backend"""
+
+# Copyright (C) PyZMQ Developers
+# Distributed under the terms of the Modified BSD License.
+
+
+import os
+import platform
+import sys
+
+from zmq.utils.sixcerpt import reraise
+
+from .select import public_api, select_backend
+
+if 'PYZMQ_BACKEND' in os.environ:
+    backend = os.environ['PYZMQ_BACKEND']
+    if backend in ('cython', 'cffi'):
+        backend = 'zmq.backend.%s' % backend
+    _ns = select_backend(backend)
+else:
+    # default to cython, fallback to cffi
+    # (reverse on PyPy)
+    if platform.python_implementation() == 'PyPy':
+        first, second = ('zmq.backend.cffi', 'zmq.backend.cython')
+    else:
+        first, second = ('zmq.backend.cython', 'zmq.backend.cffi')
+
+    try:
+        _ns = select_backend(first)
+    except Exception:
+        exc_info = sys.exc_info()
+        exc = exc_info[1]
+        try:
+            _ns = select_backend(second)
+        except ImportError:
+            # prevent 'During handling of the above exception...' on py3
+            # can't use `raise ... from` on Python 2
+            if hasattr(exc, '__cause__'):
+                exc.__cause__ = None
+            # raise the *first* error, not the fallback
+            reraise(*exc_info)
+
+globals().update(_ns)
+
+__all__ = public_api