simple question:the count of array

[sdf]

>>> a=['a','b','c']
>>> b=a.count()
Traceback (most recent call last):
  File "<pyshell#9>", line 1, in ?
    b=a.count()
TypeError: count() takes exactly 1 argument (0 given)
>>> 

then how I get the number of a,I mean how much 
values in a,in this case it should be 3 
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