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I'm trying to understand the following piece of code:
# node list
n = []
for i in xrange(1, numnodes + 1):
tmp = session.newobject();
n.append(tmp)
link(n[0], n[-1])
Specifically, I don't understand what the index -1 refers to. If the index 0 refers to the first element, then what does -1 refer to?
536
Negative numbers mean that you count from the right instead of the left. So, list[-1] refers to the last element, list[-2] is the second-last, and so on.
Negative indexing in Python means the indexing starts from the end of the iterable. The last element is at index -1, the second last at -2, and so on.
JavaScript arrays are collections of items, where each item is accessible through an index. These indexes are non-negative integers, and accessing a negative index will just return undefined . Fortunately, using Proxies, we can support accessing our array items starting from the end using negative indexes.
Python allows negative indexing for its sequences. The index of -1 refers to the last item, -2 to the second last item and so on.
Negative numbers mean that you count from the right instead of the left. So, list[-1] refers to the last element, list[-2] is the second-last, and so on.
181
List indexes of -x mean the xth item from the end of the list, so n[-1] means the last item in the list n. Any good Python tutorial should have told you this.
It's an unusual convention that only a few other languages besides Python have adopted, but it is extraordinarily useful; in any other language you'll spend a lot of time writing n[n.length-1] to access the last item of a list.
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