<p>我认为这会被认为是“Python式”的:</p>
<pre><code>for item in a[:3]:
print item
</code></pre>
<p><strong>编辑</strong>:由于几秒钟后这个答案就变得多余,我将尝试提供一些背景信息:</p>
<p><strong>数组切片允许在序列(如字符串列表)中进行快速选择。一维序列的子序列可以由左端点和右端点的索引指定:</p>
<pre><code>>>> [1,2,3,4,5][:3] # every item with an index position < 3
[1, 2, 3]
>>> [1,2,3,4,5][3:] # every item with an index position >= 3
[4, 5]
>>> [1,2,3,4,5][2:3] # every item with an index position within the interval [2,3)
[3]
</code></pre>
<p>注意左边的<a href="http://en.wikipedia.org/wiki/Interval_%28mathematics%29" rel="nofollow">endpoint is included</a>,右边的不是。您可以添加第三个参数以仅选择序列的第<code>n</code>个元素:</p>
<pre><code>>>> [1,2,3,4,5][::2] # select every second item from list
[1, 3, 5]
>>> [1,2,3,4,5][::-1] # select every single item in reverse order
[5,4,3,2,1]
>>> [1,2,3,4,5][1:4:2] # every second item from subsequence [1,4) = [2,3,4]
[2, 4]
</code></pre>
<p>通过将列表转换为<a href="http://www.numpy.org/" rel="nofollow">numpy</a>数组,甚至可以执行多维切片:</p>
<pre><code>>>> numpy.array([[1,2,3,4,5], [1,2,3,4,5]])[:, ::2]
array([[1, 3, 5],
[1, 3, 5]])
</code></pre>