是否可以使用ast.NodeVisitor两次访问Python AST中的节点或更改遍历顺序？

Question

NodeVisitor首先遍历AST深度优先,并在输入时仅访问每个节点一次.因此,做一些严肃的事情是有问题的.是否可以更改其默认行为？

Answer 1

也许有人会对一些草拟的例子感兴趣,如何做DSblizzard提出的建议,所以听到我的例子:

import ast

class RecursiveVisitor(ast.NodeVisitor):
    """ example recursive visitor """

    def recursive(func):
        """ decorator to make visitor work recursive """
        def wrapper(self,node):
            func(self,node)
            for child in ast.iter_child_nodes(node):
                self.visit(child)
        return wrapper

    @recursive
    def visit_Assign(self,node):
        """ visit a Assign node and visits it recursively"""
        print(type(node).__name__)

    @recursive
    def visit_BinOp(self, node):
        """ visit a BinOp node and visits it recursively"""
        print(type(node).__name__)

    @recursive
    def visit_Call(self,node):
        """ visit a Call node and visits it recursively"""
        print(type(node).__name__)

    @recursive
    def visit_Lambda(self,node):
        """ visit a Function node """
        print(type(node).__name__)

    @recursive
    def visit_FunctionDef(self,node):
        """ visit a Function node and visits it recursively"""
        print(type(node).__name__)

    @recursive
    def visit_Module(self,node):
        """ visit a Module node and the visits recursively"""
        pass

    def generic_visit(self,node):
        pass

class SimpleVisitor(ast.NodeVisitor):
    """ simple visitor for comparison """

    def recursive(func):
        """ decorator to make visitor work recursive """
        def wrapper(self,node):
            func(self,node)
            for child in ast.iter_child_nodes(node):
                self.visit(child)
        return wrapper

    def visit_Assign(self,node):
        """ visit a Assign node """
        print(type(node).__name__)

    def visit_BinOp(self, node):
        """ visit a BinOp node """
        print(type(node).__name__)

    def visit_Call(self,node):
        """ visit a Call node """
        print(type(node).__name__)

    def visit_Lambda(self,node):
        """ visit a Function node """
        print(type(node).__name__)

    def visit_FunctionDef(self,node):
        """ visit a Function node """
        print(type(node).__name__)

    @recursive
    def visit_Module(self,node):
        """ visit a Module node and the visits recursively, otherwise you
        wouldn't see anything here"""
        pass

    def generic_visit(self,node):
        pass

# usage example
a = """
b= lambda x: x*5 +5
def hhh(u):
    b=19
    return u*b
m=hhh(9*4+5)
"""

recursive_visitor = RecursiveVisitor()
simple_visitor = SimpleVisitor()
tree = ast.parse(a)
print('\nvisit recursive\n')
recursive_visitor.visit(tree)
print('\nvisit simple\n')
simple_visitor.visit(tree)

希望有人可能会发现它很有用.

Answer 2

没有。您应该编写自己的访问者。递归访问所有节点相当简单，因此如果 ast 模块的内容不能为您执行此操作（并且在本例中，模块中没有任何内容可以执行您想要的操作），那么您自己执行此操作也不错。