Can someone please explain how does [::-1] work? I have read somewhere that it reverses the list, I tried it and it actually works, but I do not know how. What do the 2 colons mean? I could not find anything like this in python documentations.
Also, does someone know the efficiency of this or the underlying algorithm?
It's the slice notation:
[start:stop:step]
start is the index where you start. If it's omitted, Python assumes you want to start at the beginning.stop is where you want to stop. If you omit it, Python assumes you want to go until the end.step is what the -1 is taking advantage of. 1 is the default value. 2 iterates over every other element. -1 iterates over all of the elements, but backwards.