在for循环中使用str.split时,“ValueError太多值无法解压缩”

我以前遇到过这个错误,原因很明显,但我在下面的代码片段中遇到了问题。

#!/usr/bin/python

ACL = 'group:troubleshooters:r,user:auto:rx,user:nrpe:r'

for e in ACL.split(','):
  print 'e = "%s"' % e
  print 'type during split = %s' % type(e.split(':'))
  print 'value during split:  %s' % e.split(':')
  print 'number of elements:  %d' % len(e.split(':'))
  for (one, two, three) in e.split(':'):
      print 'one = "%s", two = "%s"' % (one, two)

我添加了这些打印语句以进行调试,并确认拆分正在生成一个3元素列表,但当我尝试将其放入3个变量时,我得到:

e = "group:troubleshooters:r"
type during split = <type 'list'>
value during split:  ['group', 'troubleshooters', 'r']
number of elements:  3
Traceback (most recent call last):
  File "/tmp/python_split_test.py", line 10, in <module>
for (one, two, three) in e.split(':'):
ValueError: too many values to unpack

我错过了什么?