/usr/lib/python2.7/dist-packages/astroid/transforms.py is in python-astroid 1.6.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | # Copyright (c) 2015-2016 Claudiu Popa <pcmanticore@gmail.com>
# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER
import collections
import warnings
class TransformVisitor(object):
"""A visitor for handling transforms.
The standard approach of using it is to call
:meth:`~visit` with an *astroid* module and the class
will take care of the rest, walking the tree and running the
transforms for each encountered node.
"""
def __init__(self):
self.transforms = collections.defaultdict(list)
def _transform(self, node):
"""Call matching transforms for the given node if any and return the
transformed node.
"""
cls = node.__class__
if cls not in self.transforms:
# no transform registered for this class of node
return node
transforms = self.transforms[cls]
orig_node = node # copy the reference
for transform_func, predicate in transforms:
if predicate is None or predicate(node):
ret = transform_func(node)
# if the transformation function returns something, it's
# expected to be a replacement for the node
if ret is not None:
if node is not orig_node:
# node has already be modified by some previous
# transformation, warn about it
warnings.warn('node %s substituted multiple times' % node)
node = ret
return node
def _visit(self, node):
if hasattr(node, '_astroid_fields'):
for field in node._astroid_fields:
value = getattr(node, field)
visited = self._visit_generic(value)
setattr(node, field, visited)
return self._transform(node)
def _visit_generic(self, node):
if isinstance(node, list):
return [self._visit_generic(child) for child in node]
elif isinstance(node, tuple):
return tuple(self._visit_generic(child) for child in node)
return self._visit(node)
def register_transform(self, node_class, transform, predicate=None):
"""Register `transform(node)` function to be applied on the given
astroid's `node_class` if `predicate` is None or returns true
when called with the node as argument.
The transform function may return a value which is then used to
substitute the original node in the tree.
"""
self.transforms[node_class].append((transform, predicate))
def unregister_transform(self, node_class, transform, predicate=None):
"""Unregister the given transform."""
self.transforms[node_class].remove((transform, predicate))
def visit(self, module):
"""Walk the given astroid *tree* and transform each encountered node
Only the nodes which have transforms registered will actually
be replaced or changed.
"""
module.body = [self._visit(child) for child in module.body]
return self._transform(module)
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