What would be the best way to return the first non nan value from this list?

testList = [nan, nan, 5.5, 5.0, 5.0, 5.5, 6.0, 6.5]

edit:

nan is a float

You can use next, a generator expression, and math.isnan:

>>> from math import isnan
>>> testList = [float('nan'), float('nan'), 5.5, 5.0, 5.0, 5.5, 6.0, 6.5]
>>> next(x for x in testList if not isnan(x))
5.5
>>>