在 python 中的 Panda dataframe 中查找 numpy 数组的大小

Question

I would like to get the size of each numpy array within a panda. How do I do this? I have:

          x          y                      z
0  [1, 2, 3, 4]  [8, 9, 7]              [8, 9, 7]
1  [2, 3, 4, 8]  [9, 8, 1]  [9, 8, 1, 6, 7, 8, 9]
2     [5, 6, 7]  [3, 4, 1]              [3, 4, 1]


cars= pd.DataFrame({'x': [[1,2,3,4],[2,3,4,8],[5,6,7]],
                    'y': [[8,9,7],[9,8,1],[3,4,1]],
                    'z': [[8,9,7],[9,8,1,6,7,8,9],[3,4,1]]})

I want:

   x  y  z
0  4  3  3
1  4  3  7
2  3  3  3

I know how to get the shape and size of the entire DataFrame, but not how to combine them with size of each block.

print(cars)
print(cars.size)
print(cars.shape)

Answer 1

Use Series.str.len in DataFrame.apply for precessing all columns:

df = cars.apply(lambda x: x.str.len())
print (df)
   x  y  z
0  4  3  3
1  4  3  7
2  3  3  3

If no missing values use DataFrame.applymap for element-wise apply function len :

df = cars.applymap(len)