【python】numpy数组（array）扩充（复制）方法repeat和tile的使用

左手的ㄟ右手 2022-07-15 00:01 305阅读 0赞

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(\[\[0, 0\],

\[2, 2\],

\[4, 4\]\])

>>>

用repeat和tile扩充数组元素，例如

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1.  <span style="font-size:14px;">>>> **import** numpy as np 
2.  >>> np.arange(10) 
3.  array(\[0, 1, 2, 3, 4, 5, 6, 7, 8, 9\]) 
4.  >>> a = np.arange(10) 
5.  >>> a 
6.  array(\[0, 1, 2, 3, 4, 5, 6, 7, 8, 9\]) 
7.  >>> a.repeat(5) 
8.  array(\[0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 
9.  4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9, 
10. 9, 9, 9, 9\]) 
11. >>> a 
12. array(\[0, 1, 2, 3, 4, 5, 6, 7, 8, 9\]) 
13. >>> np.tile(a,2) 
14. array(\[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9\]) 
15. >>> </span>

官方例子：

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1.  >>> **from** numpy **import** \* 
2.  >>> a=array(\[10,20\]) 
3.  >>> tile(a,(3,2)) \#构造3X2个copy
4.  array(\[\[10, 20, 10, 20\], 
5.   \[10, 20, 10, 20\], 
6.   \[10, 20, 10, 20\]\]) 
7.  >>> tile(42.0,(3,2)) 
8.  array(\[\[ 42., 42.\], 
9.   \[ 42., 42.\], 
10.  \[ 42., 42.\]\]) 
11. >>>

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1.  >>> **from** numpy **import** \* 
2.  >>> repeat(7.,4) 
3.  array(\[ 7., 7., 7., 7.\]) 
4.  >>> a=array(\[10,20\]) 
5.  >>> a.repeat(\[3,2\]) 
6.  array(\[10, 10, 10, 20, 20\]) 
7.  >>> repeat(a,\[3,2\]) 
8.  array(\[10, 10, 10, 20, 20\]) 
9.  >>> a=array(\[\[10,20\],\[30,40\]\]) 
10. >>> a.repeat(\[3,2\],axis=0) 
11. array(\[\[10, 20\], 
12.  \[10, 20\], 
13.  \[10, 20\], 
14.  \[30, 40\], 
15.  \[30, 40\]\]) 
16. >>> a.repeat(\[3,2\],axis=1) 
17. array(\[\[10, 10, 10, 20, 20\], 
18.  \[30, 30, 30, 40, 40\]\]) 
19. >>>

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