#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You 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.
#
"""Python Callable utilities.
For internal use only; no backwards-compatibility guarantees.
"""
import importlib
[docs]class PythonCallableWithSource(object):
"""Represents a Python callable object with source codes before evaluated.
Proxy object to Store a callable object with its string form (source code).
The string form is used when the object is encoded and transferred to foreign
SDKs (non-Python SDKs).
Supported formats include fully-qualified names such as `math.sin`,
expressions such as `lambda x: x * x` or `str.upper`, and multi-line function
definitions such as `def foo(x): ...` or class definitions like
`class Foo(...): ...`. If the source string contains multiple lines then lines
prior to the last will be evaluated to provide the context in which to
evaluate the expression, for example::
import math
lambda x: x - math.sin(x)
is a valid chunk of source code.
"""
def __init__(self, source):
# type: (str) -> None
self._source = source
self._callable = self.load_from_source(source)
[docs] @classmethod
def load_from_source(cls, source):
if source in __builtins__:
return cls.load_from_expression(source)
elif all(s.isidentifier() for s in source.split('.')):
if source.split('.')[0] in __builtins__:
return cls.load_from_expression(source)
else:
return cls.load_from_fully_qualified_name(source)
else:
return cls.load_from_script(source)
[docs] @staticmethod
def load_from_expression(source):
return eval(source) # pylint: disable=eval-used
[docs] @staticmethod
def load_from_fully_qualified_name(fully_qualified_name):
o = None
path = ''
for segment in fully_qualified_name.split('.'):
path = '.'.join([path, segment]) if path else segment
if o is not None and hasattr(o, segment):
o = getattr(o, segment)
else:
o = importlib.import_module(path)
return o
[docs] @staticmethod
def load_from_script(source, method_name=None):
lines = [
line for line in source.split('\n')
if line.strip() and line.strip()[0] != '#'
]
common_indent = min(len(line) - len(line.lstrip()) for line in lines)
lines = [line[common_indent:] for line in lines]
if method_name is None:
for ix, line in reversed(list(enumerate(lines))):
if line[0] != ' ':
if line.startswith('def '):
method_name = line[4:line.index('(')].strip()
elif line.startswith('class '):
method_name = line[5:line.index('(') if '(' in
line else line.index(':')].strip()
else:
method_name = '__python_callable__'
lines[ix] = method_name + ' = ' + line
break
else:
raise ValueError("Unable to identify callable from %r" % source)
# pylint: disable=exec-used
# pylint: disable=ungrouped-imports
import apache_beam as beam
exec_globals = {'beam': beam}
exec('\n'.join(lines), exec_globals)
return exec_globals[method_name]
[docs] def default_label(self):
src = self._source.strip()
last_line = src.split('\n')[-1]
if last_line[0] != ' ' and len(last_line) < 72:
return last_line
# Avoid circular import.
from apache_beam.transforms.ptransform import label_from_callable
return label_from_callable(self._callable)
@property
def _argspec_fn(self):
return self._callable
[docs] def get_source(self):
# type: () -> str
return self._source
def __call__(self, *args, **kwargs):
return self._callable(*args, **kwargs)