python list 取重复次数

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import numpy as np   a = [1,2,3,45,6,7,123,2,1,3,4,5,123,2,3,4] def all_np(arr):     arr = np.array(arr)     key = np.unique(arr)     result = {}     for k in key:         mask = (arr == k)         arr_new = arr[mask]         v = arr_new.size         result[k] = v     return result   ret = all_np(a) print(ret) # 结果 # {1: 2, 2: 3, 3: 3, 4: 2, 5: 1, 6: 1, 7: 1, 45: 1, 123: 2}

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