I want to count the elements of a python list that is within a dataframe, and for the output to be a column in the dataframe. 我怎么做？

Question

所以，我有一個看起來像這樣的數據框：

| column_1 | column 2        |
| 0.       | [`a`, 'b', 'c'] |
| 1        | ['z', 'y']      |
| 2        | ['a']           |

我想要的 output 是一列（具有相同的索引號），如下所示：

| column_1 | column 2        | column 3|
| 0.       | [`a`, 'b', 'c'] | 3       |
| 1        | ['z', 'y']      | 2       |
| 2        | ['a']           | 1       |

Answer 1

做就是了：

df['column_3'] =  df['column_2'].apply(len)
print(df)

Output

   column_1   column_2  column_3
0         0  [a, b, c]         3
1         1     [z, y]         2
2         2        [a]         1

或者更hacky，使用str訪問器：

df['column_3'] = df['column_2'].str.len()
print(df)

Output

   column_1   column_2  column_3
0         0  [a, b, c]         3
1         1     [z, y]         2
2         2        [a]         1