blob: 3205cf0e270bff9dfc0781a8e905ce05d69e1473 [file] [log] [blame]
#!/usr/bin/env python
#
# Copyright 2010 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utility functions for use with the Google App Engine Pipeline API."""
__all__ = ["for_name", "is_generator_function"]
import inspect
import logging
def for_name(fq_name, recursive=False):
"""Find class/function/method specified by its fully qualified name.
Fully qualified can be specified as:
* <module_name>.<class_name>
* <module_name>.<function_name>
* <module_name>.<class_name>.<method_name> (an unbound method will be
returned in this case).
for_name works by doing __import__ for <module_name>, and looks for
<class_name>/<function_name> in module's __dict__/attrs. If fully qualified
name doesn't contain '.', the current module will be used.
Args:
fq_name: fully qualified name of something to find
Returns:
class object.
Raises:
ImportError: when specified module could not be loaded or the class
was not found in the module.
"""
fq_name = str(fq_name)
module_name = __name__
short_name = fq_name
if fq_name.rfind(".") >= 0:
(module_name, short_name) = (fq_name[:fq_name.rfind(".")],
fq_name[fq_name.rfind(".") + 1:])
try:
result = __import__(module_name, None, None, [short_name])
return result.__dict__[short_name]
except KeyError:
# If we're recursively inside a for_name() chain, then we want to raise
# this error as a key error so we can report the actual source of the
# problem. If we're *not* recursively being called, that means the
# module was found and the specific item could not be loaded, and thus
# we want to raise an ImportError directly.
if recursive:
raise
else:
raise ImportError("Could not find '%s' on path '%s'" % (
short_name, module_name))
except ImportError, e:
# module_name is not actually a module. Try for_name for it to figure
# out what's this.
try:
module = for_name(module_name, recursive=True)
if hasattr(module, short_name):
return getattr(module, short_name)
else:
# The module was found, but the function component is missing.
raise KeyError()
except KeyError:
raise ImportError("Could not find '%s' on path '%s'" % (
short_name, module_name))
except ImportError:
# This means recursive import attempts failed, thus we will raise the
# first ImportError we encountered, since it's likely the most accurate.
pass
# Raise the original import error that caused all of this, since it is
# likely the real cause of the overall problem.
raise
def is_generator_function(obj):
"""Return true if the object is a user-defined generator function.
Generator function objects provides same attributes as functions.
See isfunction.__doc__ for attributes listing.
Adapted from Python 2.6.
Args:
obj: an object to test.
Returns:
true if the object is generator function.
"""
CO_GENERATOR = 0x20
return bool(((inspect.isfunction(obj) or inspect.ismethod(obj)) and
obj.func_code.co_flags & CO_GENERATOR))