urlfetch 发送什么而不是 None 值?

What does urlfetch send instead of None value?

我有以下(简化的)代码:

def track_event(category, value=None):
  form_fields = {
    'ec': category,
    'ev': value
  }
  form_data = urllib.urlencode(form_fields)
  result = urlfetch.fetch(url='http://example.com',
      payload=form_data,
      method=urlfetch.POST)
  return result.status_code

track_event('category')

valueNone 时作为 ev 值发送什么?

代码使用 urllib.urlencodeNone 转换为字符串 'None':

>>> import urllib
>>> urllib.urlencode({'ev': None})
'ev=None'