node = ast.parse('a = 10')
print(astor.dump_tree(node))
# Module(body=[Assign(targets=[Name(id='a')], value=Constant(value=10, kind=None), type_comment=None)], type_ignores=[])

node = ast.parse('a = b')
print(astor.dump_tree(node.body[0]))
# Assign(targets=[Name(id='a')], value=Name(id='b'), type_comment=None)

node = ast.parse('a = 100')
print(astor.dump_tree(node.body[0]))
# Assign(targets=[Name(id='a')], value=Constant(value=100, kind=None), type_comment=None)
node = ast.parse('a = "paddle"')
print(astor.dump_tree(node.body[0]))
# Assign(targets=[Name(id='a')], value=Constant(value='paddle', kind=None), type_comment=None)

node = ast.parse('paddle.to_tensor(1, a = 10)')
print(astor.dump_tree(node.body[0]))

# Expr(
    value=Call(func=Attribute(value=Name(id='paddle'), attr='to_tensor'),
        args=[Constant(value=1, kind=None)],
        keywords=[keyword(arg='a', value=Constant(value=10, kind=None))]))

node = ast.parse('a.to_tensor(1, a = 10).reshape(1)')
print(astor.dump_tree(node.body[0]))

Expr(
    value=Call(
        func=Attribute(
            value=Call(func=Attribute(value=Name(id='a'), attr='to_tensor'),      
                args=[Constant(value=1, kind=None)],
                keywords=[keyword(arg='a', value=Constant(value=10, kind=None))]),
            attr='reshape'),
        args=[Constant(value=1, kind=None)],
        keywords=[]))

node = ast.parse('a.shape')
print(astor.dump_tree(node.body[0]))

Expr(value=Attribute(value=Name(id='a'), attr='shape'))

class NodeVisitor(object):
    def visit(self, node):
        """Visit a node."""
        method = 'visit_' + node.__class__.__name__
        visitor = getattr(self, method, self.generic_visit)
        return visitor(node)
    def generic_visit(self, node):
    	# 可以看到 generic_visit函數(shù)會調(diào)用visit函數(shù)，然后尋找并調(diào)用特定類型的visit函數(shù)。 
        """Called if no explicit visitor function exists for a node."""
        for field, value in iter_fields(node):
            if isinstance(value, list):
                for item in value:
                    if isinstance(item, AST):
                        self.visit(item)
            elif isinstance(value, AST):
                self.visit(value)
    def visit_Constant(self, node):
        value = node.value
        type_name = _const_node_type_names.get(type(value))
        if type_name is None:
            for cls, name in _const_node_type_names.items():
                if isinstance(value, cls):
                    type_name = name
                    break
        if type_name is not None:
            method = 'visit_' + type_name
            try:
                visitor = getattr(self, method)
            except AttributeError:
                pass
            else:
                import warnings
                warnings.warn(f"{method} is deprecated; add visit_Constant",
                              PendingDeprecationWarning, 2)
                return visitor(node)
        return self.generic_visit(node)

class CustomVisitor(ast.NodeVisitor):
    def visit_Attribute(self, node):
        print('----' + node.attr)
        ast.NodeVisitor.generic_visit(self, node)
    def generic_visit(self, node):
        print(node.__class__.__name__)
        ast.NodeVisitor.generic_visit(self, node)
code = textwrap.dedent(
    '''
    import paddle
    x = paddle.to_tensor([1, 2, 3])
    axis = 0
    y = paddle.max(x, axis=axis)
    '''
)
node = ast.parse(code)
visitor = CustomVisitor()
visitor.generic_visit(node)

def get_full_attr(node):
        # torch.nn.fucntional.relu
        if isinstance(node, ast.Attribute):
            return get_full_attr(node.value) + '.' + node.attr
        # x.abs() -> 'x'
        elif isinstance(node, ast.Name):
            return node.id
        # for example ast.Call
        else:
            return 'ClassMethod'
            
class CustomVisitor(ast.NodeTransformer):
    
    def visit_Call(self, node):
        # 獲取api的全稱
        full_func = get_full_attr(node.func)

        # post order
        ast.NodeVisitor.generic_visit(self, node)
        
        # 如果是普通方法調(diào)用，直接改寫整個結(jié)點即可
        if full_func == 'torch.tensor':
            # 將 torch.tensor() 改寫為 paddle.to_tensor()
            code = 'paddle.to_tensor()'
            new_node = ast.parse(code).body[0]
            return new_node.value
        
        # 如果是類方法調(diào)用，需要取前面改寫后的方法作為 func.value 
        if full_func == 'ClassMethod.floor':
            # 獲取前綴方法作為 func.value
            new_func = astor.to_source(node).strip('\n')
            new_func = new_func[0: new_func.rfind('.')]
            # 將 floor() 改寫為 floor2()
            code = '{}.{}()'.format(new_func, 'floor2')
            new_node = ast.parse(code).body[0]
            return new_node.value

        # 其余結(jié)點不修改
        return node

code = textwrap.dedent(
    '''
    import torch
    x = torch.tensor([1, 2, 3])
    x = x.exp().floor()
    '''
)
node = ast.parse(code)
visitor = CustomVisitor()
node = visitor.generic_visit(node)
result_code = astor.to_source(node)
print(result_code)