如何提取函数中引用的全局变量的名称

def extract_global_variables(func):
    global_vars = []
    for var_name, var_value in globals().items():
        if var_name != 'func' and var_name not in func.__code__.co_varnames:
            global_vars.append(var_name)
    return global_vars

import inspect

def extract_global_variables(func):
    closure_vars = inspect.getclosurevars(func)
    global_vars = []
    for var_name, var_value in closure_vars.globals.items():
        if var_name != 'func' and var_name not in func.__code__.co_varnames:
            global_vars.append(var_name)
    return global_vars

import ast

def extract_global_variables(func):
    source_code = inspect.getsource(func)
    tree = ast.parse(source_code)
    global_vars = []
    for node in ast.walk(tree):
        if isinstance(node, ast.Name) and isinstance(node.ctx, ast.Load):
            var_name = node.id
            if var_name != 'func' and var_name not in func.__code__.co_varnames:
                global_vars.append(var_name)
    return global_vars