Editing Array slicing (section)

===1991: [[Python (programming language)|Python]]===
If you have the following list:

<syntaxhighlight lang="pycon">
>>> nums = [1, 3, 5, 7, 8, 13, 20]
</syntaxhighlight>

Then it is possible to slice by using a notation similar to element retrieval:

<syntaxhighlight lang="pycon">
>>> nums[3]   # no slicing
7
>>> nums[:3]  # from index 0 (inclusive) until index 3 (exclusive)
[1, 3, 5]
>>> nums[1:5]
[3, 5, 7, 8]
>>> nums[-3:]
[8, 13, 20]
</syntaxhighlight>
Note that Python allows negative list indices. The index -1 represents the last element, -2 the penultimate element, etc.
Python also allows a step property by appending an extra colon and a value. For example:
<syntaxhighlight lang="pycon">
>>> nums[3:]
[7, 8, 13, 20]
>>> nums[3::] # == nums[3:]
[7, 8, 13, 20]
>>> nums[::3] # starting at index 0 and getting every third element
[1, 7, 20]
>>> nums[1:5:2] # from index 1 until index 5 and getting every second element
[3, 7]
</syntaxhighlight>

The stride syntax (<code>nums[1:5:2]</code>) was introduced in the second half of the 1990s, as a result of requests put forward by scientific users in the Python "matrix-SIG" (special interest group).<ref name="millman">{{cite journal |first1=K. Jarrod |last1=Millman |first2=Michael |last2=Aivazis |title=Python for Scientists and Engineers |journal=Computing in Science and Engineering |volume=13 |number=2 |pages=9–12 |year=2011 |doi=10.1109/MCSE.2011.36 |bibcode=2011CSE....13b...9M |url=http://www.computer.org/csdl/mags/cs/2011/02/mcs2011020009.html}}</ref>

Slice semantics potentially differ per object; new semantics can be introduced when [[operator overloading]] the indexing operator. With Python standard lists (which are [[dynamic array]]s), every slice is a copy. Slices of [[NumPy]] arrays, by contrast, are views onto the same underlying buffer.