python - How to check if all items in the list are None?

Question

In [27]: map( lambda f,p: f.match(p), list(patterns.itervalues()), vatids )
Out[27]: [None, <_sre.SRE_Match object at 0xb73bfdb0>, None]

The list can be all None or one of it is an re.Match instance. What one liner check can I do on the returned list to tell me that the contents are all None?

Answer 1

all(v is None for v in l)

will return True if all of the elements of l are None

Note that l.count(None) == len(l) is a lot faster but requires that l be an actual list and not just an iterable.