Two rules when reading Python (slice notation)

This time I will write about Python slice notation.

Slices are written with simple rules, but for beginners If you use it several times, you may get confused at some moments.

At that time, I will talk about two rules that you should be aware of.

■ Two rules when reading slices

① The order of data starts from 0th (basic list) ② The end of the slice will be $ n-1 $, which is one before.

I will explain it with an example.

Prepare the following data. In rule ①, the order is simply 0th, 1st, 2nd, etc. from the first data. Based on that, we will extract the numbers. As mentioned above, we were able to extract numbers based on the index number (ranking starting from 0). With this rule alone, I think it's still easy.

Next, I will explain the rule of ②. This is where the confusing problem arises. In this list, the 5th data from 0 was 10. Even if you specify up to 5th in the slice and extract, only 9 is output.

In this way, in slices, when specifying the range of index numbers Only the order up to $ n-1 $, one step before the end number, is extracted. (This time $ n = 5 $) I will actually put in other numbers and check it. If you are a beginner, you may be conscious of rule (1) and copy sutras while studying. If the above slice notation suddenly appears, you may think it complicatedly.

In that case, please think based on the two rules I mentioned at the beginning.

[Rules for reading slices] ① The order of data starts from 0th ② The end of the slice will be $ n-1 $