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I know that I can use something like string[3:4] to get a substring in Python, but what does the 3 mean in somesequence[::3]?
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Answer: The double colon is a special case in Python's extended slicing feature. The extended slicing notation string[start:stop:step] uses three arguments start , stop , and step to carve out a subsequence. It accesses every step -th element between indices start (included) and stop (excluded).
Artturi Jalli. In Python, [::-1] means reversing a string, list, or any iterable with an ordering. For example: hello = "Hello world"
Consider a python list, In-order to access a range of elements in a list, you need to slice a list. One way to do this is to use the simple slicing operator i.e. colon(:) With this operator, one can specify where to start the slicing, where to end, and specify the step.
It selects all but the last element of a sequence.
it means 'nothing for the first argument, nothing for the second, and jump by three'. It gets every third item of the sequence sliced. Extended slices is what you want. New in Python 2.3
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Python sequence slice addresses can be written as a[start:end:step] and any of start, stop or end can be dropped. a[::3] is every third element of the sequence.
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