python中统计元素出现的次数

1、

>>> a = ["cc","aa","bb","cc","aa","dd","aa","cc","ee","dd"]
>>> sorted(set(a))
['aa', 'bb', 'cc', 'dd', 'ee']
>>> b = sorted(set(a))
>>> b
['aa', 'bb', 'cc', 'dd', 'ee']
>>> for i in b:
    print(i,a.count(i))

    
aa 3
bb 1
cc 3
dd 2
ee 1

2、

>>> a = ["aa","bb","cc","aa","cc","aa","cc","aa","aa"]
>>> sorted(set(a))
['aa', 'bb', 'cc']
>>> a.count("aa")
5
>>> b = []
>>> for i in a:
    if i == "aa":
        b.append(i)

        
>>> b
['aa', 'aa', 'aa', 'aa', 'aa']
>>> len(b)
5