Source code for memote.support.gpr_helpers
# -*- coding: utf-8 -*-
# Copyright 2016 Novo Nordisk Foundation Center for Biosustainability,
# Technical University of Denmark.
#
# 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.
"""Helper classes and functions for analyzing GPR associations."""
from __future__ import absolute_import
import ast
import logging
import re
__all__ = ("find_top_level_complex",)
logger = logging.getLogger(__name__)
logical_and = re.compile(r"(and)|([&]{1,2})", flags=re.IGNORECASE)
logical_or = re.compile(r"(or)|([|]{1,2})", flags=re.IGNORECASE)
escape_chars = re.compile(r"[.-]")
class DummySet(object):
"""Define a faux set implementation."""
def add(self, value):
"""Do nothing on adding a value."""
pass
class GPRVisitor(ast.NodeVisitor):
"""
Implement a visitor that walks all nodes of an expression tree.
An abstract syntax tree (AST), generated using ``ast.parse`` on a
gene-protein-reaction (GPR) association, is traversed and the unique left
and right elements (genes) of the top level logical AND are recorded.
Due to using the ``ast`` module, precedence of Boolean operators and general
syntax requirements follow the Python standard.
Attributes
----------
left : set
After walking an AST, this attribute contains unique elements of the
left branch of the top level binary operator AND. May be empty.
right : set
After walking an AST, this attribute contains unique elements of the
right branch of the top level binary operator AND. May be empty.
Examples
--------
>>> import ast
>>> expression = ast.parse("g1 or (g2 and g3)")
>>> walker = GPRVisitor()
>>> walker.visit(expression)
>>> walker.left
{'g2'}
>>> walker.right
{'g3'}
"""
def __init__(self, **kwargs):
"""Initialize a GPR visitor."""
super(GPRVisitor, self).__init__(**kwargs)
self.left = set()
self.right = set()
self._current = DummySet()
self._is_top = True
def generic_visit(self, node):
logger.debug("%s", type(node).__name__)
super(GPRVisitor, self).generic_visit(node)
def visit_BoolOp(self, node):
"""Set up recording of elements with this hook."""
if self._is_top and isinstance(node.op, ast.And):
self._is_top = False
self._current = self.left
self.visit(node.values[0])
self._current = self.right
for successor in node.values[1:]:
self.visit(successor)
else:
self.generic_visit(node)
def visit_Name(self, node):
"""Record node names on the current branch."""
self._current.add(node.id)
[docs]def find_top_level_complex(gpr):
"""
Find unique elements of both branches of the top level logical AND.
Parameters
----------
gpr : str
The gene-protein-reaction association as a string.
Returns
-------
int
The size of the symmetric difference between the set of elements to
the left of the top level logical AND and the right set.
"""
logger.debug("%r", gpr)
conform = logical_and.sub("and", gpr)
conform = logical_or.sub("or", conform)
conform = escape_chars.sub("_", conform)
expression = ast.parse(conform)
walker = GPRVisitor()
walker.visit(expression)
return len(walker.left ^ walker.right)