从numpy ndarray中的每个维度获取某些元素

Question

How to get first element from each dimension in a numpy ndarray?

import numpy
A = numpy.array([['a','b','c'],['d','e','f'],['g','h','i']])

Result should be:

Result = ['a','d','g']

Answer 1

>>> import numpy
>>> A = numpy.array([['a','b','c'],['d','e','f'],['g','h','i']])
>>> A[:,0]
array(['a', 'd', 'g'],
      dtype='|S1')
>>> A[...,0]
array(['a', 'd', 'g'],
      dtype='|S1')

See Indexing (basic) - NumPy Manual , Indexing - NumPy Manual .

Answer 2

Did you try this?

  list( A[:,0] )

Indexing a numpy array will normally return another Numpy array, so you will need the list constructor if you need a list.

Answer 3

use the take function

import numpy
A = numpy.array([['a','b','c'],['d','e','f'],['g','h','i']])
print A.take((0,), 1)