Why do we not follow the off by one rule in python

Question

I am new learner and learning Python from a book.
I did what was written in the book....
I made a list like this below.....
 

players = ['charles', 'martina', 'michael', 'florence', 'eli']
 Then I wrote...
print(players[0:3])

#The results were like this....
['charles', 'martina', 'michael']

So my question is this.... When we write the starting number (which is 0 in this case) we follow the "off by one" rule.... but when we write 3 as the end value... we have the third element!!!! Why do we not follow the "off by one" rule here?

Answer 1

It's because of the way in which slicing notation works. [0:3] goes up to the 3rd element but does not include it. You can see this by slicing from the 3rd element until the end of the list
print(players[3:0])
#['florence, 'eli']

The 3 at the end is not the 3rd item in the list it is the 4th