Why does print("aA".count("")) print the value 3?

Question

I was working with the .count method for Strings. The count method finds the total number of occurrences of the argument inside the calling string.

But I don't understand how .count("") works. Can someone explain that?

Answer 1

There are three offsets – distances from the start of the string – where you can find an empty string: 0, 1, and 2.

| a | A |
^0  ^   ^
    |1  |
        |2

You can find an empty string at any offset for any string, of course, so s.count("") is always len(s) + 1.

Answer 2

The empty string occurs three times in "aA": once before the "a", once between the "a" and the "A" and once after the "A".