来自 python AST 的 NetworkX 图中的子图同构答案

【问题标题】：Subgraph isomorphism in NetworkX graphs from python ASTs来自 python AST 的 NetworkX 图中的子图同构
【发布时间】：2022-08-03 03:33:35
【问题描述】：

我有两个 python 文件。我生成了两个 NetworkX 图，只是遍历文件的 AST。我想检查一下 - 一个图的子图是否与另一个图同构？

Python文件如下所示 -

而test.py

a= 10
while(a <= 0):
    if a == 5:
        print(a)
        a += 1
print(\"exited\")

whiletestchanged.py

a= 10
# ANBD
\'\'\'
Test Someting
\'\'\'
while(a <= 0): #   print(\"a is:\", a)    
    if a == 5:   # if a is 5, then break  
        print(a) 
    a += 1
    # a += 1 
print(\"exited\")

从 AST 制作 NXgraphs 的类

class GetNXgraphFromAST(ast.NodeVisitor):
    def __init__(self):
        self.stack = []
        self.graph = nx.Graph()

    def generic_visit(self, stmt):
        node_name = stmt
        parent_name = None

        if self.stack:
            parent_name = self.stack[-1]

        self.stack.append(node_name)
        self.graph.add_node(node_name)

        if parent_name:
            self.graph.add_edge(node_name, parent_name)

        super(self.__class__, self).generic_visit(stmt)
        self.stack.pop()

他们的图表表示如下 -

whiletest.png

whiletestchanged.png

检查同构的代码 -

nodesoriginal = ast.parse(srcOriginal)
nodesbackport = ast.parse(srcBackport)
OriginalNXGraphIni = GetNXgraphFromAST()
BackportNXGraphIni = GetNXgraphFromAST()
OriginalNXGraphIni.visit(nodesoriginal) 
BackportNXGraphIni.visit(nodesbackport)
OriginalNXGraph = OriginalNXGraphIni.graph
BackportNXGraph = BackportNXGraphIni.graph

isomorphicSUbGraphs = isomorphism.GraphMatcher(OriginalNXGraph, BackportNXGraph)
for subGraph in isomorphicSUbGraphs.subgraph_isomorphisms_iter():
    subGraph = subGraph
    break

但它没有检测到任何子同构图。我犯了什么错误吗？提前感谢您对此提供的任何帮助。

你能提供可运行的代码吗？

标签： python networkx abstract-syntax-tree isomorphism

【解决方案1】：

下面的代码接受两个 Python 源字符串，检查是否存在任何同构子图，然后打印结果：

import ast
import collections

def tree_attrs(tree):
   #extract AST node's attributes for matching later
   return (t:=type(tree)).__name__, \
    {a:getattr(tree, a) for a in t._fields if not isinstance(getattr(tree, a), 
                                                              (ast.AST, list))}, \
    [i for i in t._fields if isinstance(getattr(tree, i), (ast.AST, list))]
    
def build_graph(tree, d1, d2, p = []):
   #recursively build subgraph from a starting AST node
   #potential child nodes can be discovered by checking d1 and d2
   if str(attrs:=tree_attrs(tree)) in d2 and \
      any(p == p1[-1*len(p):] or not p for _, p1 in d2[str(attrs)]):
      ast_attrs = {}
      for i in attrs[2]:
         if isinstance(v:=getattr(tree, i), list):
            ast_attrs[i] = [result for j in v if (result:=build_graph(j, d1, d2, p+[type(tree).__name__])) is not None]
         elif (result:=build_graph(v, d1, d2, p+[type(tree).__name__])) is not None:
            ast_attrs[i] = result
      return type(tree)(**attrs[1], **ast_attrs, **{i:getattr(tree, i, 0) 
             for i in type(tree)._attributes})   

def walk(tree, p = []):
   #get all AST nodes from the .py source, along with its ancestor hierarchy
   yield tree, p
   for i in tree._fields:
     if isinstance(v:=getattr(tree, i), list):
       for j in v:
          yield from walk(j, p + [type(tree).__name__])
     elif isinstance(v, ast.AST):
        yield from walk(v, p + [type(tree).__name__])

def subgraphs(s1, s2):
   d1, d2 = collections.defaultdict(list), collections.defaultdict(list)
   for i, p in walk(ast.parse(s1)):
      d1[str(tree_attrs(i))].append((i, p))
   for i, p in walk(ast.parse(s2)):
      d2[str(tree_attrs(i))].append((i, p))
   return [build_graph(i, d1, d2) for i in ast.walk(ast.parse(s1))]
   
def valid_py_subgraphs(sub_g):
   result = []
   for i in sub_g:
      try:
         if (r:=ast.unparse(i)):
            result.append(r)
      except: pass
   return result

s1 = """
a= 10
while(a <= 0):
    if a == 5:
        print(a)
        a += 1
print("exited")
"""
s2 = """a= 10
# ANBD
'''
Test Someting
'''
while(a <= 0): #   print("a is:", a)    
    if a == 5:   # if a is 5, then break  
        print(a) 
    a += 1
    # a += 1 
print("exited")"""
sub_g = valid_py_subgraphs(subgraphs(s1, s2))
print(bool(sub_g))
print('='*20)
for i in sub_g:
  print(i)
  print('-'*20)

样本输出：

True
====================
a = 10
while a <= 0:
    if a == 5:
        print(a)
print('exited')
--------------------
a = 10
--------------------
while a <= 0:
    if a == 5:
        print(a)
--------------------
print('exited')
--------------------
a
--------------------
10
--------------------
a <= 0
--------------------
if a == 5:
    print(a)
--------------------
print('exited')
--------------------
a += 1
--------------------
print(a)
--------------------
...

s3 = """
def main(a, b, c):
    return [i for i in range([3, 4])]
"""
s4 = """
def main(a, b, n = 10):
   return [i for i in range([1, 2, 3])]
"""
sub_g = valid_py_subgraphs(subgraphs(s3, s4))
print(bool(sub_g))
for i in sub_g:
  print(i)
  print('-'*20)

样本输出：

True
====================
def main(a, b):
    return [i for i in range([3])]
--------------------
a, b
--------------------
return [i for i in range([3])]
--------------------
a
--------------------
b
--------------------
[i for i in range([3])]
--------------------
 for i in range([3])
--------------------
i
--------------------
range([3])
--------------------
range
--------------------
[3]
--------------------
3
--------------------
...

s5 = """
def test(a:int, b:str) -> None:
   x += 1
"""
s6 = """
for i in range(10):
   print(i)
"""
sub_g = valid_py_subgraphs(subgraphs(s5, s6))
print(bool(sub_g))

输出：

False

【讨论】：