flatten是numpy.ndarray.flatten的一个函数,其官方文档是这样描述的:
ndarray.flatten(order='C')
Return a copy of the array collapsed into one dimension.
Parameters:
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order : {‘C’, ‘F’, ‘A’, ‘K’}, optional
‘C’ means to flatten in row-major (C-style) order. ‘F’ means to flatten in column-major (Fortran- style) order. ‘A’ means to flatten in column-major order if a is Fortran contiguous in memory, row-major order otherwise. ‘K’ means to flatten a in the order the elements occur in memory. The default is ‘C’.
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Returns: |
y : ndarray
A copy of the input array, flattened to one dimension.
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即返回一个折叠成一维的数组。但是该函数只能适用于numpy对象,即array或者mat,普通的list列表是不行的。
例子:
1、用于array对象
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from numpy import * >>>a = array([[ 1 , 2 ],[ 3 , 4 ],[ 5 , 6 ]]) ###此时a是一个array对象 >>>a array([[ 1 , 2 ],[ 3 , 4 ],[ 5 , 6 ]]) >>>a.flatten() array([ 1 , 2 , 3 , 4 , 5 , 6 ]) |
2、用于mat对象
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>>> a = mat([[ 1 , 2 , 3 ],[ 4 , 5 , 6 ]]) >>> a matrix([[ 1 , 2 , 3 ], [ 4 , 5 , 6 ]])<br>>>> a.flatten()<br>matrix([[ 1 , 2 , 3 , 4 , 5 , 6 ]])<br> |
3、但是该方法不能用于list对象
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>>> a = [[ 1 , 2 , 3 ],[ 4 , 5 , 6 ],[ 'a' , 'b' ]] >>> a [[ 1 , 2 , 3 ], [ 4 , 5 , 6 ], [ 'a' , 'b' ]] >>> a.flatten() ###报错 Traceback (most recent call last): File "<stdin>" , line 1 , in <module> AttributeError: 'list' object has no attribute 'flatten' |
想要list达到同样的效果可以使用列表表达式:
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>>> [y for x in a for y in x] [ 1 , 2 , 3 , 4 , 5 , 6 , 'a' , 'b' ] |