Our Engineering Team Ragged Python’s AST to Patch 100,000s of Traces of Code

import ast

def is_multi_index_rename_node(node):
    """
    Tests if the given node represents the code: .levels[].name = 
    and returns the corresponding var, idx and val if it does.
    """
    strive:
        if (
            isinstance(node, ast.Build)
            and node.targets[0].attr == "name"
            and node.targets[0].cost.cost.attr == "levels"
        ):
            var = node.targets[0].cost.cost.cost.id
            idx = node.targets[0].cost.nick.cost.n
            val = node.cost

            return Appropriate, var, idx, val
    aside from:
        pass
    return Fraudulent, None, None, None

def get_new_multi_index_rename_node(var, idx, val):
    """
    Returns AST node that represents the code:  = .set_names(, diploma=)
    for the given var, idx and val.
    """
    return ast.Build(
        targets=[ast.Name(id=var)],
        cost=ast.Name(
            func=ast.Attribute(cost=ast.Title(id=var), attr="set_names"),
            args=[val],
            keywords=[ast.keyword(arg="level", value=ast.Num(n=idx))],
        ),
    )

def patch(node):
    """
    Takes an AST rooted at the give node and patches it.
    """
    # If it is a leaf node, then no patching wanted.
    if no longer hasattr(node, "_fields"):
        return node

    # For every child of the node, modify it if wanted and recursively call patch on it.
    for (name, discipline) in ast.iter_fields(node):
        if isinstance(discipline, listing):
            for i in differ(len(discipline)):
                test, var, idx, val = is_multi_index_rename_node(discipline[i])
                if test:
                    discipline[i] = get_new_multi_index_rename_node(var, idx, val)
                else:
                    patch(discipline[i])
        else:
            test, var, idx, val = is_multi_index_rename_node(discipline)
            if test:
                setattr(node, name, get_new_multi_index_rename_node(var, idx, val))
            else:
                patch(discipline)