initial import of the packaging package in the standard library
diff --git a/Lib/packaging/pypi/wrapper.py b/Lib/packaging/pypi/wrapper.py
new file mode 100644
index 0000000..945d08a
--- /dev/null
+++ b/Lib/packaging/pypi/wrapper.py
@@ -0,0 +1,99 @@
+"""Convenient client for all PyPI APIs.
+
+This module provides a ClientWrapper class which will use the "simple"
+or XML-RPC API to request information or files from an index.
+"""
+
+from packaging.pypi import simple, xmlrpc
+
+_WRAPPER_MAPPINGS = {'get_release': 'simple',
+ 'get_releases': 'simple',
+ 'search_projects': 'simple',
+ 'get_metadata': 'xmlrpc',
+ 'get_distributions': 'simple'}
+
+_WRAPPER_INDEXES = {'xmlrpc': xmlrpc.Client,
+ 'simple': simple.Crawler}
+
+
+def switch_index_if_fails(func, wrapper):
+ """Decorator that switch of index (for instance from xmlrpc to simple)
+ if the first mirror return an empty list or raises an exception.
+ """
+ def decorator(*args, **kwargs):
+ retry = True
+ exception = None
+ methods = [func]
+ for f in wrapper._indexes.values():
+ if f != func.__self__ and hasattr(f, func.__name__):
+ methods.append(getattr(f, func.__name__))
+ for method in methods:
+ try:
+ response = method(*args, **kwargs)
+ retry = False
+ except Exception as e:
+ exception = e
+ if not retry:
+ break
+ if retry and exception:
+ raise exception
+ else:
+ return response
+ return decorator
+
+
+class ClientWrapper:
+ """Wrapper around simple and xmlrpc clients,
+
+ Choose the best implementation to use depending the needs, using the given
+ mappings.
+ If one of the indexes returns an error, tries to use others indexes.
+
+ :param index: tell which index to rely on by default.
+ :param index_classes: a dict of name:class to use as indexes.
+ :param indexes: a dict of name:index already instantiated
+ :param mappings: the mappings to use for this wrapper
+ """
+
+ def __init__(self, default_index='simple', index_classes=_WRAPPER_INDEXES,
+ indexes={}, mappings=_WRAPPER_MAPPINGS):
+ self._projects = {}
+ self._mappings = mappings
+ self._indexes = indexes
+ self._default_index = default_index
+
+ # instantiate the classes and set their _project attribute to the one
+ # of the wrapper.
+ for name, cls in index_classes.items():
+ obj = self._indexes.setdefault(name, cls())
+ obj._projects = self._projects
+ obj._index = self
+
+ def __getattr__(self, method_name):
+ """When asking for methods of the wrapper, return the implementation of
+ the wrapped classes, depending the mapping.
+
+ Decorate the methods to switch of implementation if an error occurs
+ """
+ real_method = None
+ if method_name in _WRAPPER_MAPPINGS:
+ obj = self._indexes[_WRAPPER_MAPPINGS[method_name]]
+ real_method = getattr(obj, method_name)
+ else:
+ # the method is not defined in the mappings, so we try first to get
+ # it via the default index, and rely on others if needed.
+ try:
+ real_method = getattr(self._indexes[self._default_index],
+ method_name)
+ except AttributeError:
+ other_indexes = [i for i in self._indexes
+ if i != self._default_index]
+ for index in other_indexes:
+ real_method = getattr(self._indexes[index], method_name,
+ None)
+ if real_method:
+ break
+ if real_method:
+ return switch_index_if_fails(real_method, self)
+ else:
+ raise AttributeError("No index have attribute '%s'" % method_name)