python实现将读入的多维list转为一维list的方法

>>> lines = open('test.txt').readlines()
>>> lines
['1n', '2n', '3n', '4,5n']
>>> for line in lines:
...  ll.extend(line.strip().split(','))
... 
>>> ll
['1', '2', '3', '4', '5']

>>> ll = []
>>> lines = open('test.txt').readlines()
>>> lines
['1n', '2n', '3n', '4,5n']
>>> for line in lines:
...  ll = ll + line.strip().split(',')
... 
>>> ll
['1', '2', '3', '4', '5']

>>> ll = []
>>> lines = open('test.txt').readlines()
>>> for line in lines:
...  ll.append(line.strip().split(','))
... 
>>> ll = np.array(ll)
>>> np.hstack(ll.flat)
array(['1', '2', '3', '4', '5'], 
  dtype='|S1')
>>> list(np.hstack(ll.flat))
['1', '2', '3', '4', '5']

>>> a = [1,'a']
>>> a.extend(np.array([2,'b']))
>>> a
[1, 'a', '2', 'b']
>>> a.extend([3,['c']])
>>> a
[1, 'a', '2', 'b', 3, ['c']]
>>> a = [1,'a']
>>> a.extend(np.array([2,'b']))
>>> a
[1, 'a', '2', 'b']
>>> a.extend([3,['c']])
>>> a
[1, 'a', '2', 'b', 3, ['c']]
>>> a = [1,'a']
>>> a.append(np.array([2,'b']))
>>> a
[1, 'a', array(['2', 'b'], 
  dtype='|S21')]
>>> a.append([3,['c']])
>>> a
[1, 'a', array(['2', 'b'], 
  dtype='|S21'), [3, ['c']]]

>>> a = np.array([[1,2],[3,4]])
>>> a.dtype
dtype('int64')
>>> a.flatten()
array([1, 2, 3, 4])
>>> 
>>> a = np.array([[1,2],[3,4],[5]])
>>> a.flatten()
array([[1, 2], [3, 4], [5]], dtype=object)

>>> ll = []
>>> lines = open('test.txt').readlines()
>>> lines
['1n', '2n', '3n', '4,5n']
>>> for line in lines:
...  ll.append(map(int,line.strip().split(',')))
... 
>>> ll
[[1], [2], [3], [4, 5]]