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鍍金池/ 問答/Python/ python多維數(shù)組改變?cè)刂档目樱?/span>

python多維數(shù)組改變?cè)刂档目樱?/h1> 
>>> l=[[0 for i in range(10)] for i in range(10)]
>>> l
[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> l[0][0]=23
>>> l
[[23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> n=[[0]*10 for i in range(10)]
>>> n
[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> n[0][0]=23
>>> n
[[23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> N=[[0]*10]*10
>>> N
[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> N[0][0]=23
>>> N
[[23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> arr=[0 for i in range(10)]
>>> L=[arr for i in range(10)]
>>> L
[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>> L[0][0]=23
>>> L
[[23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0], [23, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
>>>

為什么l和n能正確修改，L和N修改了每個(gè)子列表的首元素值？

回答
編輯回答
愛礙唉

因?yàn)?l 和 n 生成每個(gè)子列表都是不同的；
而 L 和 N 生成的每個(gè)子列表，都是相同的，都是指向同一個(gè)列表對(duì)象；

判斷依據(jù)，可以通過(guò)： id(l[0], l[1]) 看兩個(gè)子列表地址（l 替換成相應(yīng)的 N,n,L,l）

另外：

    對(duì)于：N = [[0] * 10 ] * 10`
    
    可以理解成：
        1. x = [0] * 10
        2. N = [x * 10]  => 很明顯，僅僅將 x 這個(gè)對(duì)象的引用復(fù)制了 10 次而已
        
   而對(duì)于：
        arr=[0 for i in range(10)]
        L=[arr for i in range(10)]
        
   這個(gè)就更好理解了，遍歷那么都次，存的還是同一個(gè)索引，這個(gè)稍微改下就能正常：
        L=[copy.copy(arr) for i in range(10)]
2017年1月4日 06:08