python之NameError:名称未在 python init 函数中定义

class HumidityServer(CoAP): 
    def __init__(self, host, port, noOfSensors=10, multicast=False): 
        CoAP.__init__(self, (host, port), multicast) 
 
        for num in range(noOfSensors): 
            self.add_resource('humidity'+num+'/', HumidityResource(num)) 

此摘录是生成以下内容的程序的一部分:

Traceback (most recent call last): 
  File "humidityserver.py", line 10, in <module> 
    class HumidityServer(CoAP): 
  File "humidityserver.py", line 14, in HumidityServer 
    for num in range(noOfSensors): 
NameError: name 'noOfSensors' is not defined 

即使我已经为变量定义了默认值，为什么会发生这种情况？