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author | Torsten Marek <shlomme@gmail.com> | 2014-11-08 23:47:14 +0100 |
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committer | Torsten Marek <shlomme@gmail.com> | 2014-11-08 23:47:14 +0100 |
commit | 477b5ee2a3d0594504ca9fc2fe0f0f9cbeccd01b (patch) | |
tree | 532231f1ecb5df4b4af6d3c12c91b684c8629673 /node_classes.py | |
parent | e10cd03c08aaf46308504330b180107e421350d6 (diff) | |
download | astroid-git-477b5ee2a3d0594504ca9fc2fe0f0f9cbeccd01b.tar.gz |
Move all astroid modules into a its own directory, which is now the package.
python setup.py develop now works.
Diffstat (limited to 'node_classes.py')
-rw-r--r-- | node_classes.py | 965 |
1 files changed, 0 insertions, 965 deletions
diff --git a/node_classes.py b/node_classes.py deleted file mode 100644 index 71e512f4..00000000 --- a/node_classes.py +++ /dev/null @@ -1,965 +0,0 @@ -# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved. -# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr -# -# This file is part of astroid. -# -# astroid is free software: you can redistribute it and/or modify it -# under the terms of the GNU Lesser General Public License as published by the -# Free Software Foundation, either version 2.1 of the License, or (at your -# option) any later version. -# -# astroid is distributed in the hope that it will be useful, but -# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or -# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License -# for more details. -# -# You should have received a copy of the GNU Lesser General Public License along -# with astroid. If not, see <http://www.gnu.org/licenses/>. -"""Module for some node classes. More nodes in scoped_nodes.py -""" - -import sys - -import six -from logilab.common.decorators import cachedproperty - -from astroid.exceptions import NoDefault -from astroid.bases import (NodeNG, Statement, Instance, InferenceContext, - _infer_stmts, YES, BUILTINS) -from astroid.mixins import (BlockRangeMixIn, AssignTypeMixin, - ParentAssignTypeMixin, FromImportMixIn) - -PY3K = sys.version_info >= (3, 0) - - -def unpack_infer(stmt, context=None): - """recursively generate nodes inferred by the given statement. - If the inferred value is a list or a tuple, recurse on the elements - """ - if isinstance(stmt, (List, Tuple)): - for elt in stmt.elts: - for infered_elt in unpack_infer(elt, context): - yield infered_elt - return - # if infered is a final node, return it and stop - infered = next(stmt.infer(context)) - if infered is stmt: - yield infered - return - # else, infer recursivly, except YES object that should be returned as is - for infered in stmt.infer(context): - if infered is YES: - yield infered - else: - for inf_inf in unpack_infer(infered, context): - yield inf_inf - - -def are_exclusive(stmt1, stmt2, exceptions=None): - """return true if the two given statements are mutually exclusive - - `exceptions` may be a list of exception names. If specified, discard If - branches and check one of the statement is in an exception handler catching - one of the given exceptions. - - algorithm : - 1) index stmt1's parents - 2) climb among stmt2's parents until we find a common parent - 3) if the common parent is a If or TryExcept statement, look if nodes are - in exclusive branches - """ - # index stmt1's parents - stmt1_parents = {} - children = {} - node = stmt1.parent - previous = stmt1 - while node: - stmt1_parents[node] = 1 - children[node] = previous - previous = node - node = node.parent - # climb among stmt2's parents until we find a common parent - node = stmt2.parent - previous = stmt2 - while node: - if node in stmt1_parents: - # if the common parent is a If or TryExcept statement, look if - # nodes are in exclusive branches - if isinstance(node, If) and exceptions is None: - if (node.locate_child(previous)[1] - is not node.locate_child(children[node])[1]): - return True - elif isinstance(node, TryExcept): - c2attr, c2node = node.locate_child(previous) - c1attr, c1node = node.locate_child(children[node]) - if c1node is not c2node: - if ((c2attr == 'body' and c1attr == 'handlers' and children[node].catch(exceptions)) or - (c2attr == 'handlers' and c1attr == 'body' and previous.catch(exceptions)) or - (c2attr == 'handlers' and c1attr == 'orelse') or - (c2attr == 'orelse' and c1attr == 'handlers')): - return True - elif c2attr == 'handlers' and c1attr == 'handlers': - return previous is not children[node] - return False - previous = node - node = node.parent - return False - - -class LookupMixIn(object): - """Mixin looking up a name in the right scope - """ - - def lookup(self, name): - """lookup a variable name - - return the scope node and the list of assignments associated to the - given name according to the scope where it has been found (locals, - globals or builtin) - - The lookup is starting from self's scope. If self is not a frame itself - and the name is found in the inner frame locals, statements will be - filtered to remove ignorable statements according to self's location - """ - return self.scope().scope_lookup(self, name) - - def ilookup(self, name): - """infered lookup - - return an iterator on infered values of the statements returned by - the lookup method - """ - frame, stmts = self.lookup(name) - return _infer_stmts(stmts, None, frame) - - def _filter_stmts(self, stmts, frame, offset): - """filter statements to remove ignorable statements. - - If self is not a frame itself and the name is found in the inner - frame locals, statements will be filtered to remove ignorable - statements according to self's location - """ - # if offset == -1, my actual frame is not the inner frame but its parent - # - # class A(B): pass - # - # we need this to resolve B correctly - if offset == -1: - myframe = self.frame().parent.frame() - else: - myframe = self.frame() - # If the frame of this node is the same as the statement - # of this node, then the node is part of a class or - # a function definition and the frame of this node should be the - # the upper frame, not the frame of the definition. - # For more information why this is important, - # see Pylint issue #295. - # For example, for 'b', the statement is the same - # as the frame / scope: - # - # def test(b=1): - # ... - - if self.statement() is myframe and myframe.parent: - myframe = myframe.parent.frame() - if not myframe is frame or self is frame: - return stmts - mystmt = self.statement() - # line filtering if we are in the same frame - # - # take care node may be missing lineno information (this is the case for - # nodes inserted for living objects) - if myframe is frame and mystmt.fromlineno is not None: - assert mystmt.fromlineno is not None, mystmt - mylineno = mystmt.fromlineno + offset - else: - # disabling lineno filtering - mylineno = 0 - _stmts = [] - _stmt_parents = [] - for node in stmts: - stmt = node.statement() - # line filtering is on and we have reached our location, break - if mylineno > 0 and stmt.fromlineno > mylineno: - break - assert hasattr(node, 'ass_type'), (node, node.scope(), - node.scope().locals) - ass_type = node.ass_type() - - if node.has_base(self): - break - - _stmts, done = ass_type._get_filtered_stmts(self, node, _stmts, mystmt) - if done: - break - - optional_assign = ass_type.optional_assign - if optional_assign and ass_type.parent_of(self): - # we are inside a loop, loop var assigment is hidding previous - # assigment - _stmts = [node] - _stmt_parents = [stmt.parent] - continue - - # XXX comment various branches below!!! - try: - pindex = _stmt_parents.index(stmt.parent) - except ValueError: - pass - else: - # we got a parent index, this means the currently visited node - # is at the same block level as a previously visited node - if _stmts[pindex].ass_type().parent_of(ass_type): - # both statements are not at the same block level - continue - # if currently visited node is following previously considered - # assignement and both are not exclusive, we can drop the - # previous one. For instance in the following code :: - # - # if a: - # x = 1 - # else: - # x = 2 - # print x - # - # we can't remove neither x = 1 nor x = 2 when looking for 'x' - # of 'print x'; while in the following :: - # - # x = 1 - # x = 2 - # print x - # - # we can remove x = 1 when we see x = 2 - # - # moreover, on loop assignment types, assignment won't - # necessarily be done if the loop has no iteration, so we don't - # want to clear previous assigments if any (hence the test on - # optional_assign) - if not (optional_assign or are_exclusive(_stmts[pindex], node)): - del _stmt_parents[pindex] - del _stmts[pindex] - if isinstance(node, AssName): - if not optional_assign and stmt.parent is mystmt.parent: - _stmts = [] - _stmt_parents = [] - elif isinstance(node, DelName): - _stmts = [] - _stmt_parents = [] - continue - if not are_exclusive(self, node): - _stmts.append(node) - _stmt_parents.append(stmt.parent) - return _stmts - -# Name classes - -class AssName(LookupMixIn, ParentAssignTypeMixin, NodeNG): - """class representing an AssName node""" - - -class DelName(LookupMixIn, ParentAssignTypeMixin, NodeNG): - """class representing a DelName node""" - - -class Name(LookupMixIn, NodeNG): - """class representing a Name node""" - - - - -##################### node classes ######################################## - -class Arguments(NodeNG, AssignTypeMixin): - """class representing an Arguments node""" - if PY3K: - # Python 3.4+ uses a different approach regarding annotations, - # each argument is a new class, _ast.arg, which exposes an - # 'annotation' attribute. In astroid though, arguments are exposed - # as is in the Arguments node and the only way to expose annotations - # is by using something similar with Python 3.3: - # - we expose 'varargannotation' and 'kwargannotation' of annotations - # of varargs and kwargs. - # - we expose 'annotation', a list with annotations for - # for each normal argument. If an argument doesn't have an - # annotation, its value will be None. - - _astroid_fields = ('args', 'defaults', 'kwonlyargs', - 'kw_defaults', 'annotations', - 'varargannotation', 'kwargannotation') - annotations = None - varargannotation = None - kwargannotation = None - else: - _astroid_fields = ('args', 'defaults', 'kwonlyargs', 'kw_defaults') - args = None - defaults = None - kwonlyargs = None - kw_defaults = None - - def __init__(self, vararg=None, kwarg=None): - self.vararg = vararg - self.kwarg = kwarg - - def _infer_name(self, frame, name): - if self.parent is frame: - return name - return None - - @cachedproperty - def fromlineno(self): - lineno = super(Arguments, self).fromlineno - return max(lineno, self.parent.fromlineno) - - def format_args(self): - """return arguments formatted as string""" - result = [] - if self.args: - result.append(_format_args(self.args, self.defaults)) - if self.vararg: - result.append('*%s' % self.vararg) - if self.kwarg: - result.append('**%s' % self.kwarg) - if self.kwonlyargs: - if not self.vararg: - result.append('*') - result.append(_format_args(self.kwonlyargs, self.kw_defaults)) - return ', '.join(result) - - def default_value(self, argname): - """return the default value for an argument - - :raise `NoDefault`: if there is no default value defined - """ - i = _find_arg(argname, self.args)[0] - if i is not None: - idx = i - (len(self.args) - len(self.defaults)) - if idx >= 0: - return self.defaults[idx] - i = _find_arg(argname, self.kwonlyargs)[0] - if i is not None and self.kw_defaults[i] is not None: - return self.kw_defaults[i] - raise NoDefault() - - def is_argument(self, name): - """return True if the name is defined in arguments""" - if name == self.vararg: - return True - if name == self.kwarg: - return True - return self.find_argname(name, True)[1] is not None - - def find_argname(self, argname, rec=False): - """return index and Name node with given name""" - if self.args: # self.args may be None in some cases (builtin function) - return _find_arg(argname, self.args, rec) - return None, None - - def get_children(self): - """override get_children to skip over None elements in kw_defaults""" - for child in super(Arguments, self).get_children(): - if child is not None: - yield child - - -def _find_arg(argname, args, rec=False): - for i, arg in enumerate(args): - if isinstance(arg, Tuple): - if rec: - found = _find_arg(argname, arg.elts) - if found[0] is not None: - return found - elif arg.name == argname: - return i, arg - return None, None - - -def _format_args(args, defaults=None): - values = [] - if args is None: - return '' - if defaults is not None: - default_offset = len(args) - len(defaults) - for i, arg in enumerate(args): - if isinstance(arg, Tuple): - values.append('(%s)' % _format_args(arg.elts)) - else: - values.append(arg.name) - if defaults is not None and i >= default_offset: - if defaults[i-default_offset] is not None: - values[-1] += '=' + defaults[i-default_offset].as_string() - return ', '.join(values) - - -class AssAttr(NodeNG, ParentAssignTypeMixin): - """class representing an AssAttr node""" - _astroid_fields = ('expr',) - expr = None - -class Assert(Statement): - """class representing an Assert node""" - _astroid_fields = ('test', 'fail',) - test = None - fail = None - -class Assign(Statement, AssignTypeMixin): - """class representing an Assign node""" - _astroid_fields = ('targets', 'value',) - targets = None - value = None - -class AugAssign(Statement, AssignTypeMixin): - """class representing an AugAssign node""" - _astroid_fields = ('target', 'value',) - target = None - value = None - -class Backquote(NodeNG): - """class representing a Backquote node""" - _astroid_fields = ('value',) - value = None - -class BinOp(NodeNG): - """class representing a BinOp node""" - _astroid_fields = ('left', 'right',) - left = None - right = None - -class BoolOp(NodeNG): - """class representing a BoolOp node""" - _astroid_fields = ('values',) - values = None - -class Break(Statement): - """class representing a Break node""" - - -class CallFunc(NodeNG): - """class representing a CallFunc node""" - _astroid_fields = ('func', 'args', 'starargs', 'kwargs') - func = None - args = None - starargs = None - kwargs = None - - def __init__(self): - self.starargs = None - self.kwargs = None - -class Compare(NodeNG): - """class representing a Compare node""" - _astroid_fields = ('left', 'ops',) - left = None - ops = None - - def get_children(self): - """override get_children for tuple fields""" - yield self.left - for _, comparator in self.ops: - yield comparator # we don't want the 'op' - - def last_child(self): - """override last_child""" - # XXX maybe if self.ops: - return self.ops[-1][1] - #return self.left - -class Comprehension(NodeNG): - """class representing a Comprehension node""" - _astroid_fields = ('target', 'iter', 'ifs') - target = None - iter = None - ifs = None - - optional_assign = True - def ass_type(self): - return self - - def _get_filtered_stmts(self, lookup_node, node, stmts, mystmt): - """method used in filter_stmts""" - if self is mystmt: - if isinstance(lookup_node, (Const, Name)): - return [lookup_node], True - - elif self.statement() is mystmt: - # original node's statement is the assignment, only keeps - # current node (gen exp, list comp) - - return [node], True - - return stmts, False - - -class Const(NodeNG, Instance): - """represent a constant node like num, str, bool, None, bytes""" - - def __init__(self, value=None): - self.value = value - - def getitem(self, index, context=None): - if isinstance(self.value, six.string_types): - return Const(self.value[index]) - raise TypeError('%r (value=%s)' % (self, self.value)) - - def has_dynamic_getattr(self): - return False - - def itered(self): - if isinstance(self.value, six.string_types): - return self.value - raise TypeError() - - def pytype(self): - return self._proxied.qname() - - -class Continue(Statement): - """class representing a Continue node""" - - -class Decorators(NodeNG): - """class representing a Decorators node""" - _astroid_fields = ('nodes',) - nodes = None - - def __init__(self, nodes=None): - self.nodes = nodes - - def scope(self): - # skip the function node to go directly to the upper level scope - return self.parent.parent.scope() - -class DelAttr(NodeNG, ParentAssignTypeMixin): - """class representing a DelAttr node""" - _astroid_fields = ('expr',) - expr = None - - -class Delete(Statement, AssignTypeMixin): - """class representing a Delete node""" - _astroid_fields = ('targets',) - targets = None - - -class Dict(NodeNG, Instance): - """class representing a Dict node""" - _astroid_fields = ('items',) - - def __init__(self, items=None): - if items is None: - self.items = [] - else: - self.items = [(const_factory(k), const_factory(v)) - for k, v in items.items()] - - def pytype(self): - return '%s.dict' % BUILTINS - - def get_children(self): - """get children of a Dict node""" - # overrides get_children - for key, value in self.items: - yield key - yield value - - def last_child(self): - """override last_child""" - if self.items: - return self.items[-1][1] - return None - - def itered(self): - return self.items[::2] - - def getitem(self, lookup_key, context=None): - for key, value in self.items: - for inferedkey in key.infer(context): - if inferedkey is YES: - continue - if isinstance(inferedkey, Const) \ - and inferedkey.value == lookup_key: - return value - # This should raise KeyError, but all call sites only catch - # IndexError. Let's leave it like that for now. - raise IndexError(lookup_key) - - -class Discard(Statement): - """class representing a Discard node""" - _astroid_fields = ('value',) - value = None - - -class Ellipsis(NodeNG): - """class representing an Ellipsis node""" - - -class EmptyNode(NodeNG): - """class representing an EmptyNode node""" - - -class ExceptHandler(Statement, AssignTypeMixin): - """class representing an ExceptHandler node""" - _astroid_fields = ('type', 'name', 'body',) - type = None - name = None - body = None - - @cachedproperty - def blockstart_tolineno(self): - if self.name: - return self.name.tolineno - elif self.type: - return self.type.tolineno - else: - return self.lineno - - def catch(self, exceptions): - if self.type is None or exceptions is None: - return True - for node in self.type.nodes_of_class(Name): - if node.name in exceptions: - return True - - -class Exec(Statement): - """class representing an Exec node""" - _astroid_fields = ('expr', 'globals', 'locals',) - expr = None - globals = None - locals = None - - -class ExtSlice(NodeNG): - """class representing an ExtSlice node""" - _astroid_fields = ('dims',) - dims = None - -class For(BlockRangeMixIn, AssignTypeMixin, Statement): - """class representing a For node""" - _astroid_fields = ('target', 'iter', 'body', 'orelse',) - target = None - iter = None - body = None - orelse = None - - optional_assign = True - @cachedproperty - def blockstart_tolineno(self): - return self.iter.tolineno - - -class From(FromImportMixIn, Statement): - """class representing a From node""" - - def __init__(self, fromname, names, level=0): - self.modname = fromname - self.names = names - self.level = level - -class Getattr(NodeNG): - """class representing a Getattr node""" - _astroid_fields = ('expr',) - expr = None - - -class Global(Statement): - """class representing a Global node""" - - def __init__(self, names): - self.names = names - - def _infer_name(self, frame, name): - return name - - -class If(BlockRangeMixIn, Statement): - """class representing an If node""" - _astroid_fields = ('test', 'body', 'orelse') - test = None - body = None - orelse = None - - @cachedproperty - def blockstart_tolineno(self): - return self.test.tolineno - - def block_range(self, lineno): - """handle block line numbers range for if statements""" - if lineno == self.body[0].fromlineno: - return lineno, lineno - if lineno <= self.body[-1].tolineno: - return lineno, self.body[-1].tolineno - return self._elsed_block_range(lineno, self.orelse, - self.body[0].fromlineno - 1) - - -class IfExp(NodeNG): - """class representing an IfExp node""" - _astroid_fields = ('test', 'body', 'orelse') - test = None - body = None - orelse = None - - -class Import(FromImportMixIn, Statement): - """class representing an Import node""" - - -class Index(NodeNG): - """class representing an Index node""" - _astroid_fields = ('value',) - value = None - - -class Keyword(NodeNG): - """class representing a Keyword node""" - _astroid_fields = ('value',) - value = None - - -class List(NodeNG, Instance, ParentAssignTypeMixin): - """class representing a List node""" - _astroid_fields = ('elts',) - - def __init__(self, elts=None): - if elts is None: - self.elts = [] - else: - self.elts = [const_factory(e) for e in elts] - - def pytype(self): - return '%s.list' % BUILTINS - - def getitem(self, index, context=None): - return self.elts[index] - - def itered(self): - return self.elts - - -class Nonlocal(Statement): - """class representing a Nonlocal node""" - - def __init__(self, names): - self.names = names - - def _infer_name(self, frame, name): - return name - - -class Pass(Statement): - """class representing a Pass node""" - - -class Print(Statement): - """class representing a Print node""" - _astroid_fields = ('dest', 'values',) - dest = None - values = None - - -class Raise(Statement): - """class representing a Raise node""" - exc = None - if sys.version_info < (3, 0): - _astroid_fields = ('exc', 'inst', 'tback') - inst = None - tback = None - else: - _astroid_fields = ('exc', 'cause') - exc = None - cause = None - - def raises_not_implemented(self): - if not self.exc: - return - for name in self.exc.nodes_of_class(Name): - if name.name == 'NotImplementedError': - return True - - -class Return(Statement): - """class representing a Return node""" - _astroid_fields = ('value',) - value = None - - -class Set(NodeNG, Instance, ParentAssignTypeMixin): - """class representing a Set node""" - _astroid_fields = ('elts',) - - def __init__(self, elts=None): - if elts is None: - self.elts = [] - else: - self.elts = [const_factory(e) for e in elts] - - def pytype(self): - return '%s.set' % BUILTINS - - def itered(self): - return self.elts - - -class Slice(NodeNG): - """class representing a Slice node""" - _astroid_fields = ('lower', 'upper', 'step') - lower = None - upper = None - step = None - -class Starred(NodeNG, ParentAssignTypeMixin): - """class representing a Starred node""" - _astroid_fields = ('value',) - value = None - - -class Subscript(NodeNG): - """class representing a Subscript node""" - _astroid_fields = ('value', 'slice') - value = None - slice = None - - -class TryExcept(BlockRangeMixIn, Statement): - """class representing a TryExcept node""" - _astroid_fields = ('body', 'handlers', 'orelse',) - body = None - handlers = None - orelse = None - - def _infer_name(self, frame, name): - return name - - def block_range(self, lineno): - """handle block line numbers range for try/except statements""" - last = None - for exhandler in self.handlers: - if exhandler.type and lineno == exhandler.type.fromlineno: - return lineno, lineno - if exhandler.body[0].fromlineno <= lineno <= exhandler.body[-1].tolineno: - return lineno, exhandler.body[-1].tolineno - if last is None: - last = exhandler.body[0].fromlineno - 1 - return self._elsed_block_range(lineno, self.orelse, last) - - -class TryFinally(BlockRangeMixIn, Statement): - """class representing a TryFinally node""" - _astroid_fields = ('body', 'finalbody',) - body = None - finalbody = None - - def block_range(self, lineno): - """handle block line numbers range for try/finally statements""" - child = self.body[0] - # py2.5 try: except: finally: - if (isinstance(child, TryExcept) and child.fromlineno == self.fromlineno - and lineno > self.fromlineno and lineno <= child.tolineno): - return child.block_range(lineno) - return self._elsed_block_range(lineno, self.finalbody) - - -class Tuple(NodeNG, Instance, ParentAssignTypeMixin): - """class representing a Tuple node""" - _astroid_fields = ('elts',) - - def __init__(self, elts=None): - if elts is None: - self.elts = [] - else: - self.elts = [const_factory(e) for e in elts] - - def pytype(self): - return '%s.tuple' % BUILTINS - - def getitem(self, index, context=None): - return self.elts[index] - - def itered(self): - return self.elts - - -class UnaryOp(NodeNG): - """class representing an UnaryOp node""" - _astroid_fields = ('operand',) - operand = None - - -class While(BlockRangeMixIn, Statement): - """class representing a While node""" - _astroid_fields = ('test', 'body', 'orelse',) - test = None - body = None - orelse = None - - @cachedproperty - def blockstart_tolineno(self): - return self.test.tolineno - - def block_range(self, lineno): - """handle block line numbers range for for and while statements""" - return self. _elsed_block_range(lineno, self.orelse) - - -class With(BlockRangeMixIn, AssignTypeMixin, Statement): - """class representing a With node""" - _astroid_fields = ('items', 'body') - items = None - body = None - - @cachedproperty - def blockstart_tolineno(self): - return self.items[-1][0].tolineno - - def get_children(self): - for expr, var in self.items: - yield expr - if var: - yield var - for elt in self.body: - yield elt - -class Yield(NodeNG): - """class representing a Yield node""" - _astroid_fields = ('value',) - value = None - -class YieldFrom(Yield): - """ Class representing a YieldFrom node. """ - -# constants ############################################################## - -CONST_CLS = { - list: List, - tuple: Tuple, - dict: Dict, - set: Set, - type(None): Const, - } - -def _update_const_classes(): - """update constant classes, so the keys of CONST_CLS can be reused""" - klasses = (bool, int, float, complex, str) - if sys.version_info < (3, 0): - klasses += (unicode, long) - if sys.version_info >= (2, 6): - klasses += (bytes,) - for kls in klasses: - CONST_CLS[kls] = Const -_update_const_classes() - -def const_factory(value): - """return an astroid node for a python value""" - # XXX we should probably be stricter here and only consider stuff in - # CONST_CLS or do better treatment: in case where value is not in CONST_CLS, - # we should rather recall the builder on this value than returning an empty - # node (another option being that const_factory shouldn't be called with something - # not in CONST_CLS) - assert not isinstance(value, NodeNG) - try: - return CONST_CLS[value.__class__](value) - except (KeyError, AttributeError): - node = EmptyNode() - node.object = value - return node |