I don't understand this result

[buran]

extend changes the list in place (and thus return None)

>>> f = [].extend(['spam', 32, 44])
>>> type(f)
<type 'NoneType'>
>>> f=[]
>>> f.extend(['spam', 32, 4])
>>> type(f)
<type 'list'>
>>> print f
['spam', 32, 4]