>>> import Qwt4 as Qwt
>>> import numpy as NP
>>> a = Qwt.QwtArrayDouble(NP.arange(10, 20, 4))
>>> for i in a:                                  # thanks to __getitem__
...  print i
...
10.0
14.0
18.0
>>> for i in range(len(a)):                      # thanks to __len__
...  print a[i]                                  # thanks to __getitem__
...
10.0
14.0
18.0
>>> for i in range(len(a)):                      # thanks to __len__
...  a[i] = 10+3*i                               # thanks to __setitem__
...
>>> for i in a:                                  # thanks to __getitem__
...  print i
...
10.0
13.0
16.0
>>>
