python以数组为参数的函数_Python中reshape函数参数1的意思？

numpy.reshape(a, newshape, order&＃61;&＃39;C&＃39;)[source]&＃xff0c;参数&＃96;newshape&＃96;是啥意思&＃xff1f;newshape : int or tuple of ints

The new shape should be compatible with the original shape. If an integer, then the result will be a 1-D array of that length. One shape dimension can be -1. In this case, **the value is inferred from the length of the array and remaining dimensions**.

大意是说&＃xff0c;数组新的shape属性应该要与原来的配套&＃xff0c;如果等于-1的话&＃xff0c;那么Numpy会根据剩下的维度计算出数组的另外一个shape属性值。

举几个例子或许就清楚了&＃xff0c;有一个数组z&＃xff0c;它的shape属性是(4, 4)

z &＃61; np.array([[1, 2, 3, 4],

[5, 6, 7, 8],

[9, 10, 11, 12],

[13, 14, 15, 16]])

z.shape

(4, 4)z.reshape(-1)

z.reshape(-1)

array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16])z.reshape(-1, 1)

也就是说&＃xff0c;先前我们不知道z的shape属性是多少&＃xff0c;但是想让z变成只有一列&＃xff0c;行数不知道多少&＃xff0c;通过&＃96;z.reshape(-1,1)&＃96;&＃xff0c;Numpy自动计算出有12行&＃xff0c;新的数组shape属性为(16, 1)&＃xff0c;与原来的(4, 4)配套。

z.reshape(-1,1)

array([[ 1],

[ 2],

[ 3],

[ 4],

[ 5],

[ 6],

[ 7],

[ 8],

[ 9],

[10],

[11],

[12],

[13],

[14],

[15],

[16]])z.reshape(-1, 2)

newshape等于-1&＃xff0c;列数等于2&＃xff0c;行数未知&＃xff0c;reshape后的shape等于(8, 2)

z.reshape(-1, 2)

array([[ 1, 2],

[ 3, 4],

[ 5, 6],

[ 7, 8],

[ 9, 10],

[11, 12],

[13, 14],

[15, 16]])

同理&＃xff0c;只给定行数&＃xff0c;newshape等于-1&＃xff0c;Numpy也可以自动计算出新数组的列数。

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