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When any of the indexes are omitted, Python uses reasonable defaults:
This code is similar to
Indices can also be negative, to indicate positions from the end of the list (i.e., from right to left.)
A third index indicates the interval or step by which items are retrieved. The default is 1, so every item is included in the result.
Since this third index can also be a negative number, the following code returns the elements from right to left.
The procedure is the same for strings. Each character is considered an item:
How to Get a Subset of a List, Tuple or String
Since lists, tuples and strings are ordered collections of objects, they support an operation called slicing. Slicing lets you get a subset of a collection by giving start and end indexes between square brackets and separated by colons:>>> languages = ["Python", "C", "C++", "Java", "Elixir", "Rust"]
>>> languages[2:4]
['C++', 'Java']
When any of the indexes are omitted, Python uses reasonable defaults:
>>> languages[1:] # All elements except the first.
['C', 'C++', 'Java', 'Elixir', 'Rust']
This code is similar to
languages[1:len(languages)].Indices can also be negative, to indicate positions from the end of the list (i.e., from right to left.)
>>> languages[:-1] # All elements except the last one.
['Python', 'C', 'C++', 'Java', 'Elixir']
A third index indicates the interval or step by which items are retrieved. The default is 1, so every item is included in the result.
>>> languages[::2] # Fetch elements every 2 steps.
['Python', 'C++', 'Elixir']
>>> list(range(1, 11))[::2]
[1, 3, 5, 7, 9]
Since this third index can also be a negative number, the following code returns the elements from right to left.
>>> languages[::-1]
['Rust', 'Elixir', 'Java', 'C++', 'C', 'Python']
The procedure is the same for strings. Each character is considered an item:
>>> s = "Hello world!"
>>> s[5:10]
'world'
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