repeat和tile扩充数组

但是很多情况下不需要使用,在进行矩阵加减运算的时候会自动复制

>>> a

array([[1, 2],

       [3, 4],

       [5, 6]])

>>> b

array([1, 2])

>>> a-b

array([[0, 0],

       [2, 2],

       [4, 4]])

>>> import numpy as np>>> np.arange(10)array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])>>> a = np.arange(10)>>> aarray([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])>>> a.repeat(5)array([0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4,       4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9,       9, 9, 9, 9])>>> aarray([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])>>> np.tile(a,2)array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9])>>>官方例子：
    >>> from numpy import *      >>> a=array([10,20])      >>> tile(a,(3,2)) #构造3X2个copy      array([[10, 20, 10, 20],             [10, 20, 10, 20],             [10, 20, 10, 20]])      >>> tile(42.0,(3,2))      array([[ 42.,  42.],             [ 42.,  42.],             [ 42.,  42.]])  
    >>> from numpy import *      >>> repeat(7.,4)      array([ 7.,  7.,  7.,  7.])      >>> a=array([10,20])      >>> a.repeat([3,2])      array([10, 10, 10, 20, 20])      >>> repeat(a,[3,2])      array([10, 10, 10, 20, 20])      >>> a=array([[10,20],[30,40]])      >>> a.repeat([3,2],axis=0)      array([[10, 20],             [10, 20],             [10, 20],             [30, 40],             [30, 40]])      >>> a.repeat([3,2],axis=1)      array([[10, 10, 10, 20, 20],             [30, 30, 30, 40, 40]])