为什么我不能通过列表理解来索引数组？

Question

为什么numpy数组可以通过列表索引，但不能通过列表推导索引？

lst = np.array(lst = ["a","b","c","d"])

ind = [i for i in range(4) if i%2 == 0]

# Indexing by the list works
lst[ind]

Out[28]: 
array(['a', 'c'], 
      dtype='|S1')


# Trying to use the list comprehension without storing it in an object first does not

lst[i for i in range(4) if i%2 == 0]

  File "<ipython-input-29-6256b805fa19>", line 1
    lst[i for i in range(4) if i%2 == 0]
            ^
SyntaxError: invalid syntax

Answer 1

您只需要一组额外的括号来“包含”列表理解：

lst[[i for i in range(4) if i%2 == 0]]