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copied!<p>Enumerating the possibilities allowed by the grammar:</p> <pre><code>>>> seq[:] # [seq[0], seq[1], ..., seq[-1] ] >>> seq[low:] # [seq[low], seq[low+1], ..., seq[-1] ] >>> seq[:high] # [seq[0], seq[1], ..., seq[high-1]] >>> seq[low:high] # [seq[low], seq[low+1], ..., seq[high-1]] >>> seq[::stride] # [seq[0], seq[stride], ..., seq[-1] ] >>> seq[low::stride] # [seq[low], seq[low+stride], ..., seq[-1] ] >>> seq[:high:stride] # [seq[0], seq[stride], ..., seq[high-1]] >>> seq[low:high:stride] # [seq[low], seq[low+stride], ..., seq[high-1]] </code></pre> <p>Of course, if <code>(high-low)%stride != 0</code>, then the end point will be a little lower than <code>high-1</code>.</p> <p>If <code>stride</code> is negative, the ordering is changed a bit since we're counting down:</p> <pre><code>>>> seq[::-stride] # [seq[-1], seq[-1-stride], ..., seq[0] ] >>> seq[high::-stride] # [seq[high], seq[high-stride], ..., seq[0] ] >>> seq[:low:-stride] # [seq[-1], seq[-1-stride], ..., seq[low+1]] >>> seq[high:low:-stride] # [seq[high], seq[high-stride], ..., seq[low+1]] </code></pre> <p>Extended slicing (with commas and ellipses) are mostly used only by special data structures (like Numpy); the basic sequences don't support them.</p> <pre><code>>>> class slicee: ... def __getitem__(self, item): ... return `item` ... >>> slicee()[0, 1:2, ::5, ...] '(0, slice(1, 2, None), slice(None, None, 5), Ellipsis)' </code></pre>

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