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在 Tornado Web 服务器的处理程序中，我有以下代码：

class NetworkSensorsHandler(BaseHandler):
# Requires authentication 
@tornado.web.authenticated
@tornado.web.removeslash
def get(self, nid):
    # Mandatory argument action = ['view' | 'edit']
    # Used only for visualization purposes
    action = self.get_argument('action').lower()
    if action not in ['view', 'edit']:
        raise tornado.web.HTTPError(404, "Unknown action: " + str(action))
    # Retrieve the current user 
    usr = self.get_current_user()
    usr_id = usr['id']

    self.lock_tables("read", ['nets_permissions as n'])
    perm = self.db.get("SELECT n.perm FROM nets_permissions as n \
                          WHERE n.network_id=%s AND n.user_id=%s", nid, int(usr_id))
    self.unlock_tables()

    # Check whether the user has access to the network
    perms = self.check_network_access(nid, perm['perm'])

    self.lock_tables("read", ['devices'])
    # Retrieve the sensors 
    sens = self.db.query("SELECT * FROM devices \
                          WHERE network_id=%s", nid)
    self.unlock_tables()
    # get network info
    net = self.get_network(nid);
    # get the permissions on the network
    writeable = self.get_network_access(net.id, PERM_WRITE)
    #s['commands'] = sensors_config[net['ntype']][s['type']]['commands']
    sens_config = sensors_config[net.ntype]

    # Retrieve the current user 
    net_id = net['id']

    # Retrieve the current rights
    self.lock_tables("read", ['users as u', 'nets_permissions as m'])
    user = self.db.query("SELECT u.id, u.name, n.perm FROM users as u LEFT OUTER JOIN (SELECT * FROM nets_permissions as m WHERE network_id=%s) as n on u.id = n.user_id WHERE (n.perm <> 3 or n.perm is NULL)", int(net_id))
    self.unlock_tables()      

    # Render the networks page
    self.render("sensors.html", sensors=sens, perms=perms, net=net, action=action, writeable=writeable, sens_config=sens_config, users=user)

现在在 html 页面中，我有一部分代码是这样的：

 {% for sens in sensors %}
 .............
 {% end %}

但很明显，当我有一些传感器然后我删除它们时，在最后一次传感器删除后我得到这个错误：

UnboundLocalError：分配前引用的局部变量“sens”

因为我认为 Tornado 中的 sens 数组是空的。如果我在数据库表中手动添加一个传感器，页面工作正常！

如果我将 if...end 块放在 {% if sensors %}...{% end %} 块中是相同的，因为页面没有同时识别变量 sens。

如果查询结果 sens 为空，如何排除 if...end 语句中的部分？或者我必须在 Tornado 处理程序中初始化 sens 变量？

非常感谢。请帮我！

编辑

完整的回溯是这样的：

Traceback (most recent call last):


 File "/usr/lib/python2.6/site-packages/tornado/web.py", line 988, in _execute
    getattr(self, self.request.method.lower())(*args, **kwargs)
  File "/usr/lib/python2.6/site-packages/tornado/web.py", line 1739, in wrapper
    return method(self, *args, **kwargs)
  File "/usr/lib/python2.6/site-packages/tornado/web.py", line 1096, in wrapper
    return method(self, *args, **kwargs)
  File "./wsn.py", line 699, in get
    self.render("sensors.html", sensors=sens, perms=perms, net=net, action=action, writeable=writeable, sens_config=sens_config, users=user)
  File "./wsn.py", line 349, in render
    tornado.web.RequestHandler.render(self, *args, **kwargs)
  File "/usr/lib/python2.6/site-packages/tornado/web.py", line 474, in render
    html = self.render_string(template_name, **kwargs)
  File "/usr/lib/python2.6/site-packages/tornado/web.py", line 586, in render_string
    return t.generate(**args)
  File "/usr/lib/python2.6/site-packages/tornado/template.py", line 253, in generate
    return execute()
  File "sensors_html.generated.py", line 363, in _execute
    _tmp = sens.id  # sensors.html:203 (via base.html:152)
UnboundLocalError: local variable 'sens' referenced before assignment
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1 回答 1

1

您能否输入完整的 HTML 或验证您的 sensors.html 中的第 203 行是否在您的“for”循环之间。

{% for sens in sensors %}
............. # line 203
{% end %}
于 2012-11-16T11:50:20.137 回答